Fix TestAccFirebaseAppHostingBackend (#13395)

Author: rainshen49

mmv1/products/firebaseapphosting/Backend.yaml

@@ -31,14 +31,22 @@ examples:
     primary_resource_id: example
     vars:
       backend_id: "mini"
+      service_act_id: "firebase-app-hosting-compute"
     test_env_vars:
       project_id: "PROJECT_NAME"
+    test_vars_overrides:
+      # prevent tests from colliding with each other
+      service_act_id: '"tf-test-fah-minimal"'
   - name: firebase_app_hosting_backend_full
     primary_resource_id: example
     vars:
       backend_id: "full"
+      service_act_id: "firebase-app-hosting-compute"
     test_env_vars:
       project_id: "PROJECT_NAME"
+    test_vars_overrides:
+      # prevent tests from colliding with each other
+      service_act_id: '"tf-test-fah-full"'
   - name: firebase_app_hosting_backend_github
     primary_resource_id: example
     vars:

mmv1/templates/terraform/examples/firebase_app_hosting_backend_full.tf.tmpl

@@ -26,7 +26,7 @@ resource "google_service_account" "service_account" {
   project = "{{index $.TestEnvVars "project_id"}}"
 
   # Must be firebase-app-hosting-compute
-  account_id                   = "firebase-app-hosting-compute"
+  account_id                   = "{{index $.Vars "service_act_id"}}"
   display_name                 = "Firebase App Hosting compute service account"
 
   # Do not throw if already exists

mmv1/templates/terraform/examples/firebase_app_hosting_backend_minimal.tf.tmpl

@@ -16,7 +16,7 @@ resource "google_service_account" "service_account" {
   project = "{{index $.TestEnvVars "project_id"}}"
 
   # Must be firebase-app-hosting-compute
-  account_id                   = "firebase-app-hosting-compute"
+  account_id                   = "{{index $.Vars "service_act_id"}}"
   display_name                 = "Firebase App Hosting compute service account"
 
   # Do not throw if already exists