Add deadLetterPolicy to Pub/Sub subscription resource

products/pubsub/api.yaml

@@ -244,3 +244,44 @@ objects:
               If ttl is not set, the associated resource never expires.
               A duration in seconds with up to nine fractional digits, terminated by 's'.
               Example - "3.5s".
+      - !ruby/object:Api::Type::NestedObject
+        name: 'deadLetterPolicy'
+        allow_empty_object: true
+        send_empty_value: true
+        description: |
+          A policy that specifies the conditions for dead lettering messages in
+          this subscription. If dead_letter_policy is not set, dead lettering
+          is disabled.
+          
+          The Cloud Pub/Sub service account associated with this subscriptions's
+          parent project (i.e.,\nservice-{project_number}@gcp-sa-pubsub.iam.gserviceaccount.com) must have
+          permission to Acknowledge() messages on this subscription.
+        properties:
+          - !ruby/object:Api::Type::String
+            name: 'deadLetterTopic'
+            description: |
+              The name of the topic to which dead letter messages should be published.
+              Format is `projects/{project}/topics/{topic}`.
+
+              The Cloud Pub/Sub service\naccount 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.
+          - !ruby/object:Api::Type::Integer
+            name: 'maxDeliveryAttempts'
+            description: |
+              The maximum number of delivery attempts for any message. The value must be
+              between 5 and 100.
+              
+              The number of delivery attempts is defined as 1 + (the sum of number of 
+              NACKs and number of times the acknowledgement deadline has been exceeded for the message).
+              
+              A NACK is any call to ModifyAckDeadline with a 0 deadline. Note that
+              client libraries may automatically extend ack_deadlines.
+              
+              This field will be honored on a best effort basis.
+            
+              If this parameter is 0, a default value of 5 is used.