add dlq information to message's systemProperties (#64)

* add dlq information to message's systemProperties

* do the rename work

* do the rename work
diff --git a/apache/rocketmq/v2/definition.proto b/apache/rocketmq/v2/definition.proto
index f0a637d..d10418d 100644
--- a/apache/rocketmq/v2/definition.proto
+++ b/apache/rocketmq/v2/definition.proto
@@ -266,6 +266,16 @@
   // orphan. Servers that manages orphan messages would pick up
   // a capable publisher to resolve
   optional google.protobuf.Duration orphaned_transaction_recovery_duration = 19;
+
+  // Information to identify whether this message is from dead letter queue.
+  optional DeadLetterQueue dead_letter_queue = 20;
+}
+
+message DeadLetterQueue {
+  // Original topic for this DLQ message.
+  string topic = 1;
+  // Original message id for this DLQ message.
+  string message_id = 2;
 }
 
 message Message {