aws_elasticache_subnet_group.default[0] will be created even if we pass elasticache_subnet_group_name

[flightlesstux]

Describe the Bug

aws_elasticache_subnet_group.default[0] will be created even if we pass elasticache_subnet_group_name

Expected Behavior

If we pass elasticache_subnet_group_name, the aws_elasticache_subnet_group.default[0] won't be created anymore

Steps to Reproduce

Just pass the vpc elasticache subnet group name as a variable.

Screenshots

  # aws_elasticache_cluster.default[0] will be created
  + resource "aws_elasticache_cluster" "default" {
      + apply_immediately            = true
      + arn                          = (known after apply)
      + auto_minor_version_upgrade   = "true"
      + availability_zone            = (known after apply)
      + az_mode                      = "single-az"
      + cache_nodes                  = (known after apply)
      + cluster_address              = (known after apply)
      + cluster_id                   = "dev-memcached"
      + configuration_endpoint       = (known after apply)
      + engine                       = "memcached"
      + engine_version               = "1.6.22"
      + engine_version_actual        = (known after apply)
      + id                           = (known after apply)
      + ip_discovery                 = (known after apply)
      + maintenance_window           = "wed:03:00-wed:04:00"
      + network_type                 = (known after apply)
      + node_type                    = "cache.t4g.micro"
      + num_cache_nodes              = 1
      + parameter_group_name         = "dev-memcached"
      + port                         = 11211
      + preferred_availability_zones = [
          + "eu-central-1a",
        ]
      + preferred_outpost_arn        = (known after apply)
      + replication_group_id         = (known after apply)
      + security_group_ids           = [
          + "sg-xxx",
        ]
      + snapshot_window              = (known after apply)
      + subnet_group_name            = "dev-vpc"
      + tags                         = {
          + "Environment" = "dev"
          + "Name"        = "dev-memcached"
        }
      + tags_all                     = {
          + "Environment"  = "dev"
          + "Name"         = "dev-memcached"
          + "map-migrated" = "xxx"
          + "terraform"    = "true"
        }
      + transit_encryption_enabled   = false
    }

  # aws_elasticache_subnet_group.default[0] will be created
  + resource "aws_elasticache_subnet_group" "default" {
      + arn         = (known after apply)
      + description = "Managed by Terraform"
      + id          = (known after apply)
      + name        = "dev-memcached"
      + subnet_ids  = [
          + "subnet-xxx",
          + "subnet-xxx",
          + "subnet-xxx",
        ]
      + tags_all    = {
          + "map-migrated" = "xxx"
          + "terraform"    = "true"
        }
      + vpc_id      = (known after apply)
    }

Environment

• OS: devops-infra/aws-latest docker image on any kind of host
• Module version: 0.19.2
• OpenTofu: 1.7.0
• Terragrunt: 0.58.2

Additional Context

If you approve quickly, I'll open a PR ASAP. The solution is easy.