azd should support terraform workspaces

[jongio]

Terraform developers are accustomed to using terraform workspaces to configure different resources for different environments.

We should natively support this in azd.

https://developer.hashicorp.com/terraform/language/state/workspaces

[jongio]

I hacked terraform workspace support like this:

main.tf

locals {
  workspace            = var.workspace
  is_default_workspace = local.workspace == "default"
}

main.tfvars.json

{
  "workspace": "${WORKSPACE=default}"
}

variables.tf

variable "workspace" {
  description = "value of workspace"
  type        = string
  default     = "dev"
}

preprovision.sh script to set the workspace

TF_WORKSPACE_DIR="${GITHUB_WORKSPACE:+$GITHUB_WORKSPACE/}.azure/${AZURE_ENV_NAME}/infra/.terraform"

# Create the directory if it doesn't exist
mkdir -p "$TF_WORKSPACE_DIR"

# Use the variable with the terraform command
terraform -chdir="$TF_WORKSPACE_DIR" workspace select -or-create "$WORKSPACE"

Then when a user wants to switch workspaces they would run

azd env set WORKSPACE azure

And conditionally provision resources like this:

resource "azurecaf_name" "aks_name" {
  count         = local.is_default_workspace ? 0 : 1
  name          = local.resource_token
  resource_type = "azurerm_kubernetes_cluster"
  random_length = 0
  clean_input   = true
}

When you do that you need to ref the conditional resources by index like this:

  queue_id = azurerm_servicebus_queue.sb_queue[0].id

You also want to use try when accessing a resource that is dependent on another resource so TF doesn't fail.

  count    = try(local.is_default_workspace ? 0 : 1, 0)