Add force_delete for notification channel

mmv1/products/monitoring/terraform.yaml

@@ -63,6 +63,7 @@ overrides: !ruby/object:Overrides::ResourceOverrides
   NotificationChannel: !ruby/object:Overrides::Terraform::ResourceOverride
     id_format: "{{name}}"
     import_format: ["{{name}}"]
+    delete_url: 'v3/{{name}}?force={{force_delete}}'
     mutex: stackdriver/notifications/{{project}}
     error_retry_predicates: ["isMonitoringConcurrentEditError"]
     examples:
@@ -78,6 +79,17 @@ overrides: !ruby/object:Overrides::ResourceOverrides
         skip_test: true
         vars:
           display_name: "Sensitive Notification Channel test"
+    virtual_fields:
+      - !ruby/object:Api::Type::Boolean
+        name: 'force_delete'
+        url_param_only: true
+        default_value: false
+        description: |
+          If true, the notification channel will be deleted regardless
+          of its use in alert policies (the policies will be updated
+          to remove the channel). If false, channels that are still
+          referenced by an existing alerting policy will fail to be
+          deleted in a delete operation.
     custom_code: !ruby/object:Provider::Terraform::CustomCode
       resource_definition: templates/terraform/resource_definition/monitoring_notification_channel.erb
       encoder: templates/terraform/encoders/monitoring_notification_channel.go.erb

mmv1/templates/terraform/examples/notification_channel_basic.tf.erb

@@ -4,4 +4,5 @@ resource "google_monitoring_notification_channel" "<%= ctx[:primary_resource_id]
   labels = {
     email_address = "fake_email@blahblah.com"
   }
+  force_delete = false
 }