fix: update service_account_id output variable (#486)

Author: q2w

modules/instance_template/main.tf

@@ -18,6 +18,12 @@
 # Locals
 #########
 
+data "google_service_account" "existing_sa" {
+  provider   = google-beta
+  count      = local.create_service_account == false ? 1 : 0
+  account_id = google_compute_instance_template.tpl.service_account[0].email
+}
+
 locals {
   source_image         = var.source_image != "" ? var.source_image : "rocky-linux-9-optimized-gcp-v20240111"
   source_image_family  = var.source_image_family != "" ? var.source_image_family : "rocky-linux-9-optimized-gcp"
@@ -80,7 +86,11 @@ locals {
     id     = google_service_account.sa[0].account_id,
     email  = google_service_account.sa[0].email,
     member = google_service_account.sa[0].member
-  } : {}
+    } : {
+    id     = data.google_service_account.existing_sa[0].account_id,
+    email  = data.google_service_account.existing_sa[0].email,
+    member = data.google_service_account.existing_sa[0].member
+  }
 }
 
 # Service account

modules/instance_template/metadata.yaml

@@ -365,6 +365,11 @@ spec:
               version: ^10.0
             spec:
               outputExpr: "[\"roles/bigquery.dataEditor\"]"
+          - source:
+              source: github.com/GoogleCloudPlatform/terraform-google-bigtable
+              version: ">= 0.1.0"
+            spec:
+              outputExpr: "[\"roles/bigtable.admin\"]"
       - name: enable_shielded_vm
         description: Whether to enable the Shielded VM configuration on the instance. Note that the instance image must support Shielded VMs. See https://cloud.google.com/compute/docs/images
         varType: bool