Workload identity module doesn't declare kubernetes provider dependency

[jackwhelpton]

cf.:

https://github.com/terraform-google-modules/terraform-google-kubernetes-engine/blob/master/modules/workload-identity/versions.tf

terraform {
  required_version = ">= 0.13.0"

  provider_meta "google" {
    module_name = "blueprints/terraform/terraform-google-kubernetes-engine:workload-identity/v16.0.1"
  }
}

with, e.g.:

https://github.com/terraform-google-modules/terraform-google-kubernetes-engine/blob/master/modules/private-cluster/versions.tf

terraform {
  required_version = ">=0.13"

  required_providers {
    google = {
      source  = "hashicorp/google"
      version = ">= 3.39.0, <4.0.0"
    }
    kubernetes = {
      source  = "hashicorp/kubernetes"
      version = "~> 2.0"
    }
  }
  provider_meta "google" {
    module_name = "blueprints/terraform/terraform-google-kubernetes-engine:private-cluster/v16.0.1"
  }
}

With TF 1.0.4, this results in warnings in the logs:

│ Warning: Provider kubernetes is undefined
│ 
│   on kubernetes.tf line 7, in module "workload_identity_blah":
│    7:     kubernetes = kubernetes.blah
│ 
│ Module module.workload_identity_blah does not declare a provider named
│ kubernetes.
│ If you wish to specify a provider configuration for the module, add an
│ entry for kubernetes in the required_providers block within the module.
│ 
│ (and one more similar warning elsewhere)

[bharathkkb]

Thanks for the report @jackwhelpton. Also happy to review a PR adding this.

[jackwhelpton]

Great, thanks; I'm happy to do this, but I don't have a detailed knowledge of what the minimum/maximum version constraints should be.