resourceIdentity: set MutableIdentity to true by default (GoogleCloudPlatform#17030)

Author: BBBmau

mmv1/templates/terraform/resource.go.tmpl

@@ -202,6 +202,9 @@ func Resource{{ $.ResourceName -}}() *schema.Resource {
           },
 {{- end }}
         },
+        ResourceBehavior: schema.ResourceBehavior{
+            MutableIdentity: true,
+        },
 {{- end }}
 
         Schema: map[string]*schema.Schema{