deadLetterTopic

The name of the topic to which dead letter messages should be published. Format is projects/{project}/topics/{topic}. The Cloud Pub/Sub service account associated with the enclosing subscription's parent project (i.e., service-{project_number}@gcp-sa-pubsub.iam.gserviceaccount.com) must have permission to Publish() to this topic. The operation will fail if the topic does not exist. Users should ensure that there is a subscription attached to this topic since messages published to a topic with no subscriptions are lost.