Convenience command to retrieve OIDC Issuer thumbprint

[yorinasub17]

Currently setting up the IAM Role for Service Accounts feature in Terraform is a bit of a pain because there is no easy way to retrieve the OIDC issuer thumbprint for setting up the provider. This adds the functionality into kubergrunt so that it can be used as an external data source:

resource "aws_eks_cluster" "example" {
  # ... other configuration ...
}

data "external" "oidc_thumbprint" {
  program = ["kubergrunt", "eks", "oidc-thumbprint", "--issuer-url", aws_eks_cluster.example.identity.0.oidc.0.issuer]
}

resource "aws_iam_openid_connect_provider" "example" {
  client_id_list  = ["sts.amazonaws.com"]
  thumbprint_list = [data.external.oidc_thumbprint.result.thumbprint]
  url             = "${aws_eks_cluster.example.identity.0.oidc.0.issuer}"
}

[brikis98]

Very nice 👍

[yorinasub17]

Thanks for the review! Will merge and release this now.