Expose the new secret_sync_config setting to enable allow synchronize secrets to Kubernetes Secrets in all modules

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TL;DR

The google_container_cluster resource has the option to enable the new (beta) secret_sync_config so that we can Synchronize secrets to Kubernetes Secrets.

Currently the UI does not expose it as well, so we had to enable it manually using:

gcloud --project <project name> \
  beta container clusters update <cluster name> \
  --location=<cluster location> \
  --enable-secret-sync

This took about 20-30 minutes to enable, but now we are able to create the SecretSync resources.

apiVersion: secret-sync.gke.io/v1
kind: SecretSync
metadata:
  name: some-secret
spec:
  serviceAccountName: some-sa
  secretProviderClassName: some-secret
  secretObject:
    type: Opaque
    data:
      - sourcePath: "foo"
        targetKey: "BAR"

It seems this feature will be "enabled" somewhere around Q1 26 (source)

Terraform Resources

https://registry.terraform.io/providers/hashicorp/google/7.14.1/docs/resources/container_cluster#secret_sync_config-2

Detailed design

Allow us consumers to enable this feature in IaC before GA

Additional information

No response