fix: support custom service account for autopilot (terraform-google-modules#1550)

Author: JeremyOT

autogen/main/cluster.tf.tmpl

@@ -162,7 +162,7 @@ resource "google_container_cluster" "primary" {
  {% if autopilot_cluster == true %}
  cluster_autoscaling {
  dynamic "auto_provisioning_defaults" {
- for_each = var.create_service_account ? [1] : []
+ for_each = (var.create_service_account || var.service_account != "") ? [1] : []
 
  content {
  service_account = local.service_account

modules/beta-autopilot-private-cluster/cluster.tf

@@ -71,7 +71,7 @@ resource "google_container_cluster" "primary" {
 
  cluster_autoscaling {
  dynamic "auto_provisioning_defaults" {
- for_each = var.create_service_account ? [1] : []
+ for_each = (var.create_service_account || var.service_account != "") ? [1] : []
 
  content {
  service_account = local.service_account

modules/beta-autopilot-public-cluster/cluster.tf

@@ -71,7 +71,7 @@ resource "google_container_cluster" "primary" {
 
  cluster_autoscaling {
  dynamic "auto_provisioning_defaults" {
- for_each = var.create_service_account ? [1] : []
+ for_each = (var.create_service_account || var.service_account != "") ? [1] : []
 
  content {
  service_account = local.service_account