Missing IAP configuration for LB

[krisero]

Currently when I would like to add OIDC (IAP):

• I cannot add Signed Header Audience JWT in TF configuration. AFAIU it can only be done via system-admin panel.

• Additionally, there is missing configuration in LB for OIDC and after setting up IAP, this change is override by terraform apply.

  Terraform planned the following actions, but then encountered a problem:
  
  # module.wandb.module.app_lb.module.url_map.google_compute_backend_service.default will be updated in-place
  ~ resource "google_compute_backend_service" "default" {
      id                              = "projects/***/global/backendServices/wandb-gke-ingress"
      name                            = "wandb-gke-ingress"
      # (17 unchanged attributes hidden)
  
    - iap {
        - oauth2_client_id            = "***.apps.googleusercontent.com" -> null
        - oauth2_client_secret_sha256 = (sensitive value) -> null
      }
  
      # (2 unchanged blocks hidden)
  }