## what
* Introduce var.data_tiering_enabled and plumb it through to the aws provider

## why
* We need to set `data_tiering_enabled` true to provision our desired node type [![DEVOPS-2155](https://img.shields.io/badge/DEVOPS-2155-blue.svg)](https://teikametrics.atlassian.net/browse/DEVOPS-2155)
* This flag `data_tiering_enabled` doesn't currently exist in the `terraform-aws-elasticache-redis` module
* After verifying this change, we plan to send it back upstream in a PR to https://github.com/cloudposse/terraform-aws-elasticache-redis

## testing

Against @teikametrics/bid-orchestratorcloudposse#202, made locally the following changes:

```diff
diff --git a/terraform-redis-bidder-common/redis.tf b/terraform-redis-bidder-common/redis.tf
index fc582ae..1bdb9df 100644
--- a/terraform-redis-bidder-common/redis.tf
+++ b/terraform-redis-bidder-common/redis.tf
@@ -48,7 +48,7 @@ resource "random_password" "password" {
 module "redis" {
   # https://registry.terraform.io/modules/cloudposse/elasticache-redis/aws/latest
   # source  = "cloudposse/elasticache-redis/aws" ## FIXME: DEVOPS-2155
-  source  = "git@github.com:teikametrics/terraform-aws-elasticache-redis.git"
+  source  = "git@github.com:teikametrics/terraform-aws-elasticache-redis.git?ref=bml.DEVOPS-2155.cloudposse-fork-data-tiering"
   # Auth token for password protecting redis, `transit_encryption_enabled` must be set to `true`.
   auth_token = random_password.password.result
   name       = var.redis_name
@@ -63,7 +63,7 @@ module "redis" {
   automatic_failover_enabled = var.redis_automatic_failover
   cluster_size               = var.redis_cluster_size
   # Must be set to true to enable data tiering
-  # data_tiering_enabled       = var.redis_data_tiering ## FIXME: DEVOPS-2155
+  data_tiering_enabled       = var.redis_data_tiering
   # The instance class used --> https://docs.aws.amazon.com/AmazonElastiCache/latest/red-ug/CacheNodes.SupportedTypes.html
   instance_type = var.redis_instance_type
   # Apply changes immediately
```

Staging plan reports no changes (because `redis_data_tiering` is false in staging); production plan reports the same currently-unapplied changes as before, plus including `data_tiering_enabled`. Previously the plan errored out as this module did not support the flag.

## terraform plans

### Staging

`tm-terraform staging staging plan`

```
No changes. Infrastructure is up-to-date.
```

### Production

`tm-terraform production production plan`

```
Terraform will perform the following actions:

  # module.redis.aws_elasticache_parameter_group.default[0] will be updated in-place
  ~ resource "aws_elasticache_parameter_group" "default" {
        id          = "bidder-redis-cluster-production"
        name        = "bidder-redis-cluster-production"
      ~ tags        = {
          + "Name"                               = "bidder-redis-cluster-production"
          + "teikametrics.com/app"               = "bid-orchestrator"
          + "teikametrics.com/deploy/stage"      = "production"
          + "teikametrics.com/name"              = "bidder-redis-cluster-production"
          + "teikametrics.com/team"              = "artificial-intelligence"
          + "teikametrics.com/terraform/gitpath" = "teikametrics/bid-orchestrator/terraform-redis"
        }
      ~ tags_all    = {
          + "Name"                               = "bidder-redis-cluster-production"
          + "teikametrics.com/app"               = "bid-orchestrator"
          + "teikametrics.com/deploy/stage"      = "production"
          + "teikametrics.com/name"              = "bidder-redis-cluster-production"
          + "teikametrics.com/team"              = "artificial-intelligence"
          + "teikametrics.com/terraform/gitpath" = "teikametrics/bid-orchestrator/terraform-redis"
        }
        # (3 unchanged attributes hidden)

        # (1 unchanged block hidden)
    }

  # module.redis.aws_elasticache_replication_group.default[0] will be created
  + resource "aws_elasticache_replication_group" "default" {
      + apply_immediately              = true
      + arn                            = (known after apply)
      + at_rest_encryption_enabled     = false
      + auth_token                     = (sensitive value)
      + auto_minor_version_upgrade     = (known after apply)
      + automatic_failover_enabled     = true
      + cluster_enabled                = (known after apply)
      + configuration_endpoint_address = (known after apply)
      + data_tiering_enabled           = true
      + description                    = "bidder-redis-cluster-production"
      + engine                         = "redis"
      + engine_version                 = "6.x"
      + engine_version_actual          = (known after apply)
      + global_replication_group_id    = (known after apply)
      + id                             = (known after apply)
      + maintenance_window             = "sun:03:00-sun:04:00"
      + member_clusters                = (known after apply)
      + multi_az_enabled               = false
      + node_type                      = "cache.r6gd.xlarge"
      + num_cache_clusters             = (known after apply)
      + num_node_groups                = 2
      + number_cache_clusters          = (known after apply)
      + parameter_group_name           = "bidder-redis-cluster-production"
      + port                           = 6379
      + primary_endpoint_address       = (known after apply)
      + reader_endpoint_address        = (known after apply)
      + replicas_per_node_group        = 1
      + replication_group_description  = (known after apply)
      + replication_group_id           = "bidder-redis-cluster-production"
      + security_group_ids             = (known after apply)
      + security_group_names           = (known after apply)
      + snapshot_retention_limit       = 7
      + snapshot_window                = "04:00-05:00"
      + subnet_group_name              = "bidder-redis-cluster-production"
      + tags                           = {
          + "Name"                               = "bidder-redis-cluster-production"
          + "teikametrics.com/app"               = "bid-orchestrator"
          + "teikametrics.com/deploy/stage"      = "production"
          + "teikametrics.com/name"              = "bidder-redis-cluster-production"
          + "teikametrics.com/team"              = "artificial-intelligence"
          + "teikametrics.com/terraform/gitpath" = "teikametrics/bid-orchestrator/terraform-redis"
        }
      + tags_all                       = {
          + "Name"                               = "bidder-redis-cluster-production"
          + "teikametrics.com/app"               = "bid-orchestrator"
          + "teikametrics.com/deploy/stage"      = "production"
          + "teikametrics.com/name"              = "bidder-redis-cluster-production"
          + "teikametrics.com/team"              = "artificial-intelligence"
          + "teikametrics.com/terraform/gitpath" = "teikametrics/bid-orchestrator/terraform-redis"
        }
      + transit_encryption_enabled     = true

      + cluster_mode {
          + num_node_groups         = (known after apply)
          + replicas_per_node_group = (known after apply)
        }
    }

  # module.redis.aws_elasticache_subnet_group.default[0] will be updated in-place
  ~ resource "aws_elasticache_subnet_group" "default" {
      ~ description = "Managed by Terraform" -> "Elasticache subnet group for bidder-redis-cluster-production"
        id          = "bidder-redis-cluster-production"
        name        = "bidder-redis-cluster-production"
      ~ tags        = {
          + "Name"                               = "bidder-redis-cluster-production"
          + "teikametrics.com/app"               = "bid-orchestrator"
          + "teikametrics.com/deploy/stage"      = "production"
          + "teikametrics.com/name"              = "bidder-redis-cluster-production"
          + "teikametrics.com/team"              = "artificial-intelligence"
          + "teikametrics.com/terraform/gitpath" = "teikametrics/bid-orchestrator/terraform-redis"
        }
      ~ tags_all    = {
          + "Name"                               = "bidder-redis-cluster-production"
          + "teikametrics.com/app"               = "bid-orchestrator"
          + "teikametrics.com/deploy/stage"      = "production"
          + "teikametrics.com/name"              = "bidder-redis-cluster-production"
          + "teikametrics.com/team"              = "artificial-intelligence"
          + "teikametrics.com/terraform/gitpath" = "teikametrics/bid-orchestrator/terraform-redis"
        }
        # (2 unchanged attributes hidden)
    }

  # module.redis.module.aws_security_group.aws_security_group.cbd[0] will be created
  + resource "aws_security_group" "cbd" {
      + arn                    = (known after apply)
      + description            = "Security group for Elasticache Redis"
      + egress                 = (known after apply)
      + id                     = (known after apply)
      + ingress                = (known after apply)
      + name                   = (known after apply)
      + name_prefix            = "bidder-redis-cluster-production-"
      + owner_id               = (known after apply)
      + revoke_rules_on_delete = false
      + tags                   = {
          + "Name"                               = "bidder-redis-cluster-production"
          + "teikametrics.com/app"               = "bid-orchestrator"
          + "teikametrics.com/deploy/stage"      = "production"
          + "teikametrics.com/name"              = "bidder-redis-cluster-production"
          + "teikametrics.com/team"              = "artificial-intelligence"
          + "teikametrics.com/terraform/gitpath" = "teikametrics/bid-orchestrator/terraform-redis"
        }
      + tags_all               = {
          + "Name"                               = "bidder-redis-cluster-production"
          + "teikametrics.com/app"               = "bid-orchestrator"
          + "teikametrics.com/deploy/stage"      = "production"
          + "teikametrics.com/name"              = "bidder-redis-cluster-production"
          + "teikametrics.com/team"              = "artificial-intelligence"
          + "teikametrics.com/terraform/gitpath" = "teikametrics/bid-orchestrator/terraform-redis"
        }
      + vpc_id                 = "vpc-0134131a45fbf70e6"

      + timeouts {
          + create = "10m"
          + delete = "15m"
        }
    }

  # module.redis.module.aws_security_group.aws_security_group_rule.keyed["_allow_all_egress_"] will be created
  + resource "aws_security_group_rule" "keyed" {
      + cidr_blocks              = [
          + "0.0.0.0/0",
        ]
      + description              = "Allow all egress"
      + from_port                = 0
      + id                       = (known after apply)
      + ipv6_cidr_blocks         = [
          + "::/0",
        ]
      + prefix_list_ids          = []
      + protocol                 = "-1"
      + security_group_id        = (known after apply)
      + self                     = false
      + source_security_group_id = (known after apply)
      + to_port                  = 0
      + type                     = "egress"
    }

  # module.redis.module.aws_security_group.aws_security_group_rule.keyed["extra[0]"] will be created
  + resource "aws_security_group_rule" "keyed" {
      + cidr_blocks              = [
          + "10.76.0.0/16",
          + "10.60.0.0/16",
          + "10.78.0.0/16",
          + "10.30.0.0/16",
        ]
      + description              = "Allow TCP inbound traffic on port 6379 from Convox and the vpc which is hosting this redis."
      + from_port                = 6379
      + id                       = (known after apply)
      + prefix_list_ids          = []
      + protocol                 = "tcp"
      + security_group_id        = (known after apply)
      + self                     = false
      + source_security_group_id = (known after apply)
      + to_port                  = 6379
      + type                     = "ingress"
    }

  # module.redis.module.security_group.aws_security_group.default[0] will be destroyed
  - resource "aws_security_group" "default" {
      - arn                    = "arn:aws:ec2:us-east-1:659641375152:security-group/sg-02edcb2360f6895b0" -> null
      - description            = "ElastiCache Security Group" -> null
      - egress                 = [
          - {
              - cidr_blocks      = [
                  - "0.0.0.0/0",
                ]
              - description      = "Allow all outbound traffic"
              - from_port        = 0
              - ipv6_cidr_blocks = []
              - prefix_list_ids  = []
              - protocol         = "-1"
              - security_groups  = []
              - self             = false
              - to_port          = 0
            },
        ] -> null
      - id                     = "sg-02edcb2360f6895b0" -> null
      - ingress                = [
          - {
              - cidr_blocks      = [
                  - "10.76.0.0/16",
                  - "10.60.0.0/16",
                  - "10.78.0.0/16",
                  - "10.30.0.0/16",
                ]
              - description      = "Allow TCP inbound traffic on port 6379 from Convox and the vpc which is hosting this redis."
              - from_port        = 6379
              - ipv6_cidr_blocks = []
              - prefix_list_ids  = []
              - protocol         = "tcp"
              - security_groups  = []
              - self             = false
              - to_port          = 6379
            },
        ] -> null
      - name                   = "bidder-redis-cluster-production" -> null
      - owner_id               = "659641375152" -> null
      - revoke_rules_on_delete = false -> null
      - tags                   = {
          - "Name"                               = "bidder-redis-cluster-production"
          - "teikametrics.com/app"               = "bid-orchestrator"
          - "teikametrics.com/deploy/stage"      = "production"
          - "teikametrics.com/name"              = "bidder-redis-cluster-production"
          - "teikametrics.com/team"              = "artificial-intelligence"
          - "teikametrics.com/terraform/gitpath" = "teikametrics/bid-orchestrator/terraform-redis"
        } -> null
      - tags_all               = {
          - "Name"                               = "bidder-redis-cluster-production"
          - "teikametrics.com/app"               = "bid-orchestrator"
          - "teikametrics.com/deploy/stage"      = "production"
          - "teikametrics.com/name"              = "bidder-redis-cluster-production"
          - "teikametrics.com/team"              = "artificial-intelligence"
          - "teikametrics.com/terraform/gitpath" = "teikametrics/bid-orchestrator/terraform-redis"
        } -> null
      - vpc_id                 = "vpc-0134131a45fbf70e6" -> null
    }

  # module.redis.module.security_group.aws_security_group_rule.default["egress--1-0-0-9c87e5e1ed040a443ce1ac8e6d6cf159"] will be destroyed
  - resource "aws_security_group_rule" "default" {
      - cidr_blocks       = [
          - "0.0.0.0/0",
        ] -> null
      - description       = "Allow all outbound traffic" -> null
      - from_port         = 0 -> null
      - id                = "sgrule-3785251229" -> null
      - protocol          = "-1" -> null
      - security_group_id = "sg-02edcb2360f6895b0" -> null
      - self              = false -> null
      - to_port           = 0 -> null
      - type              = "egress" -> null
    }

  # module.redis.module.security_group.aws_security_group_rule.default["ingress-tcp-6379-6379-c992040fb21cf75967d80aa440691f00"] will be destroyed
  - resource "aws_security_group_rule" "default" {
      - cidr_blocks       = [
          - "10.76.0.0/16",
          - "10.60.0.0/16",
          - "10.78.0.0/16",
          - "10.30.0.0/16",
        ] -> null
      - description       = "Allow TCP inbound traffic on port 6379 from Convox and the vpc which is hosting this redis." -> null
      - from_port         = 6379 -> null
      - id                = "sgrule-236626820" -> null
      - protocol          = "tcp" -> null
      - security_group_id = "sg-02edcb2360f6895b0" -> null
      - self              = false -> null
      - to_port           = 6379 -> null
      - type              = "ingress" -> null
    }

Plan: 4 to add, 2 to change, 3 to destroy.

Changes to Outputs:
  + redis_master_endpoint = (known after apply)

```

## references
* https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/elasticache_replication_group#data_tiering_enabled

Co-authored-by: nitrocode <7775707+nitrocode@users.noreply.github.com>

…che-redis