Add 'delivery_attempt' field in the Cloud Pub/Sub data schema.

PiperOrigin-RevId: 702756217

Author: yoshi-code-bot

proto/google/events/cloud/pubsub/v1/data.proto

@@ -31,6 +31,18 @@ message MessagePublishedData {
   // generated. The format of the value is
   // `projects/{project-id}/subscriptions/{subscription-id}`.
   string subscription = 2;
+
+  // The approximate number of times that Pub/Sub has attempted to deliver
+  // the associated message to a subscriber.
+  //
+  // More precisely, this is 1 + (number of NACKs) +
+  // (number of ack_deadline exceeds) for this message.
+  //
+  // Upon the first delivery of a given message, `delivery_attempt` will have a
+  // value of 1. The value is calculated at best effort and is approximate.
+  //
+  // If a DeadLetterPolicy is not set on the subscription, this will be 0.
+  int32 delivery_attempt = 3;
 }
 
 // A message published to a topic.