fix: Manage route tables for multiple database subnets

[y-batsianouski]

Description

Module fails when I try to create multiple database subnets with create_database_subnet_route_table = true and single_nat_gateway = false

Motivation and Context

When I try to create multiple database subnets with it's own route tables, module tries to create:

1. multiple db subnets
2. One route table for multiple database subnets
3. Multiple routes for each NAT gateway. Points all this routes to one route table and fails.

Breaking Changes

There was no possibility to create multiple db subnets with create_database_subnet_route_table = true and single_nat_gateway = false. So there are shouldn't be breaking changes.

How Has This Been Tested?

Case 1

module "vpc-test" {
  ...
  cidr             = "10.40.0.0/16"
  azs              = ["us-east-1a", "us-east-1b"]
  public_subnets   = ["10.40.1.0/24", "10.40.2.0/24"]
  private_subnets  = ["10.40.3.0/24", "10.40.4.0/24"]
  database_subnets = ["10.40.5.0/24", "10.40.6.0/24"]

  single_nat_gateway                     = false
  create_database_subnet_route_table     = true
  create_database_nat_gateway_route      = true
  ...
}

Creates 2 route tables for database subnets. Points each route table to appropriate NAT gateway

Case 2

module "vpc-test" {
  ...
  cidr             = "10.40.0.0/16"
  azs              = ["us-east-1a", "us-east-1b"]
  public_subnets   = ["10.40.1.0/24", "10.40.2.0/24"]
  private_subnets  = ["10.40.3.0/24", "10.40.4.0/24"]
  database_subnets = ["10.40.5.0/24", "10.40.6.0/24"]

  single_nat_gateway                     = true
  create_database_subnet_route_table     = true
  create_database_nat_gateway_route      = true
  ...
}

Creates 1 route table for all database subnets. Points route table to single NAT gateway

Case 3

module "vpc-test" {
  ...
  cidr             = "10.40.0.0/16"
  azs              = ["us-east-1a", "us-east-1b"]
  public_subnets   = ["10.40.1.0/24", "10.40.2.0/24"]
  private_subnets  = ["10.40.3.0/24", "10.40.4.0/24"]
  database_subnets = ["10.40.5.0/24", "10.40.6.0/24"]
  
  create_database_subnet_route_table     = true
  create_database_nat_gateway_route      = false
  create_database_internet_gateway_route = true
  ...
}

Creates 1 route table for all database subnets. Points route table to internet gateway

[DrFaust92]

Looks good to me, ill try to test all the cases.

[y-batsianouski]

@antonbabenko @DrFaust92 Did you have a chance to look at this? Thanks!

[Chili-Man]

@y-batsianouski Can you please update this with the base branch?

@antonbabenko @DrFaust92 I can confirm that this fixes the issue I reported #516

[y-batsianouski]

@y-batsianouski Can you please update this with the base branch?

@antonbabenko @DrFaust92 I can confirm that this fixes the issue I reported #516

@Chili-Man I'll try to manage this soon. But It's not very interesting for me now because I've written my own tf module for VPC which was inspired by this module but provides much more flexibility: https://registry.terraform.io/modules/y-batsianouski/vpc/aws.
Unfortunately full documentation isn't completed yet, but I'm going to update it soon.

[Chili-Man]

@y-batsianouski I understand, thanks for the update; I can carry this forward then; I'll open a new pr with these changes

[Chili-Man]

@y-batsianouski @antonbabenko @DrFaust92 I've opened this pr to carry the changes forward here: #518 . Feel free to close this PR

[y-batsianouski]

Closining. @Chili-Man handover this changes in it's PR: #518

[bryantbiggs]

hi all, this is fixed now in #518

[github-actions]

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