Disambiguate consul backing store names to help during migration

[gc-ss]

Feature Description

I currently have a consul cluster per environment and I use consul as the backing store for Terraform.
Often, after certain internal milestones/checkpoints, I change the consul cluster that Terraform is configured to use.
When this happens, the migration message output from Terraform confuses me.

For example, assume:

• I have consul_cluster_a and consul_cluster_b.
• the current OSS Terraform workspace uses consul_cluster_a as the backing store
• after a while, I have to change the backing store from consul_cluster_a to consul_cluster_b
• Then I see the following migration message:

Do you want to migrate all workspaces to "consul"?
  Both the existing "consul" backend and the newly configured "consul" backend
  support workspaces. When migrating between backends, Terraform will copy
  all workspaces (with the same names). THIS WILL OVERWRITE any conflicting
  states in the destination.

  Terraform initialization doesn't currently migrate only select workspaces.
  If you want to migrate a select number of workspaces, you must manually
  pull and push those states.

  If you answer "yes", Terraform will migrate all states. If you answer
  "no", Terraform will abort.

This is very confusing, to me, as I have no idea which consul_cluster_a or consul_cluster_b is being mentioned when it says "consul" in:

Do you want to migrate all workspaces to "consul"?
  Both the existing "consul" backend and the newly configured "consul" backend
  support workspaces. When migrating between backends, Terraform will copy

I would have preferred to see, something more explicit like:

Do you want to migrate all workspaces to "consul_cluster_b"?
  Both the existing "consul_cluster_a" backend and the newly configured "consul_cluster_b" backend
  support workspaces. When migrating between backends, Terraform will copy

My current definition block looks like this:

    backend "consul" {
      …
    }

1. Is there something I can modify to get the behavior I want?
2. Is this possible at all?

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[gc-ss]

Moved to hashicorp/terraform-provider-consul#275