Add "detached" bool to Subscription

PiperOrigin-RevId: 314795690

google/pubsub/v1/pubsub.proto

@@ -724,6 +724,13 @@ message Subscription {
   // RetryPolicy will be triggered on NACKs or acknowledgement deadline
   // exceeded events for a given message.
   RetryPolicy retry_policy = 14;
+
+  // Indicates whether the subscription is detached from its topic. Detached
+  // subscriptions don't receive messages from their topic and don't retain any
+  // backlog. `Pull` and `StreamingPull` requests will return
+  // FAILED_PRECONDITION. If the subscription is a push subscription, pushes to
+  // the endpoint will not be made.
+  bool detached = 15;
 }
 
 // A policy that specifies how Cloud Pub/Sub retries message delivery.