feat: Default to clusters OIDC issuer URL for aws_eks_identity_provider_config

[igorbrites]

Description

(I'm thinking if this should be a PR or an Issue, but I'm not too good to describe things, so here is the PR 😄).

Nowadays, to create an aws_eks_identity_provider_config using the module, we need to pass the issuer_url:

module "eks" {
  # ...
  cluster_identity_providers = {
    default = {
      client_id  = "sts.amazonaws.com"
      issuer_url = "https://oidc.eks.us-east-1.amazonaws.com/id/A1B2C3D4E5F6G7H8I9J0"
    }
  }
}

But this value is already present on the cluster, and we can't self-reference the value on the module, nor use data sources to set this value when creating a new cluster.

So, I think we could pass the cluster's OIDC issuer URL as the default parameter to the aws_eks_identity_provider_config resource.

Or I understood this wrong, which is a possibility 😬. If so, how do you guys create aws_eks_identity_provider_configs?

Motivation and Context

Removes the need to create aws_eks_identity_provider_config outside the module.

Breaking Changes

It does not break any version.

How Has This Been Tested?

• I have updated at least one of the examples/* to demonstrate and validate my change(s)
• I have tested and validated these changes using one or more of the provided examples/* projects

• I have executed pre-commit run -a on my pull request

[bryantbiggs]

Thank you @igorbrites !

[antonbabenko]

This PR is included in version 18.27.0 🎉

[github-actions]

I'm going to lock this pull request because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues. If you have found a problem that seems related to this change, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.

[bryantbiggs]

FYI - this default behavior is being reverted starting in 1.30 since it is incorrect and the upstream K8s project is tightening up authentication #3055