Add comment about using request message ID for correlation

HTTP over AMQP 1.0 extension specification, 5.1:
To associate a response with a request, the correlation-id value of the response properties
MUST be set to the message-id value of the request properties.

Author: acogoluegnes

src/main/java/com/rabbitmq/client/amqp/impl/AmqpManagement.java

@@ -41,6 +41,15 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+/**
+ * Follow the <a
+ * href="https://github.com/oasis-tcs/amqp-specs/blob/master/http-over-amqp-v1.0-wd06a.docx">HTTP
+ * Semantics and Content over AMQP Version 1.0</a> extension specification.
+ *
+ * @see <a
+ *     href="https://github.com/oasis-tcs/amqp-specs/blob/master/http-over-amqp-v1.0-wd06a.docx">HTTP
+ *     Semantics and Content over AMQP Version 1.0</a>
+ */
 class AmqpManagement implements Management {
 
   private static final AtomicLong ID_SEQUENCE = new AtomicLong(0);
@@ -341,8 +350,7 @@ private Response<Map<String, Object>> declare(
     checkAvailable();
     UUID requestId = messageId();
     try {
-      Message<?> request =
-          Message.create(body).messageId(requestId).to(target).subject(operation).replyTo(REPLY_TO);
+      Message<?> request = Message.create(body).to(target).subject(operation);
 
       OutstandingRequest outstandingRequest = this.request(request, requestId);
       outstandingRequest.block();
@@ -355,6 +363,10 @@ private Response<Map<String, Object>> declare(
   }
 
   OutstandingRequest request(Message<?> request, UUID requestId) throws ClientException {
+    // HTTP over AMQP 1.0 extension specification, 5.1:
+    // To associate a response with a request, the correlation-id value of the response properties
+    // MUST be set to the message-id value of the request properties.
+    request.messageId(requestId).replyTo(REPLY_TO);
     OutstandingRequest outstandingRequest = new OutstandingRequest(this.rpcTimeout);
     LOGGER.debug("Enqueueing request {}", requestId);
     this.outstandingRequests.put(requestId, outstandingRequest);
@@ -382,12 +394,7 @@ private Map<String, Object> delete(String target, int expectedResponseCode) {
     checkAvailable();
     UUID requestId = messageId();
     try {
-      Message<?> request =
-          Message.create((Map<?, ?>) null)
-              .messageId(requestId)
-              .to(target)
-              .subject(DELETE)
-              .replyTo(REPLY_TO);
+      Message<?> request = Message.create((Map<?, ?>) null).to(target).subject(DELETE);
 
       OutstandingRequest outstandingRequest = request(request, requestId);
       outstandingRequest.block();
@@ -497,12 +504,7 @@ private static Optional<String> matchBinding(
   private OutstandingRequest get(String target) throws ClientException {
     checkAvailable();
     UUID requestId = messageId();
-    Message<?> request =
-        Message.create((Map<?, ?>) null)
-            .messageId(requestId)
-            .to(target)
-            .subject(GET)
-            .replyTo(REPLY_TO);
+    Message<?> request = Message.create((Map<?, ?>) null).to(target).subject(GET);
 
     OutstandingRequest outstandingRequest = request(request, requestId);
     outstandingRequest.block();

src/main/java/com/rabbitmq/client/amqp/impl/AmqpRpcClient.java

@@ -100,6 +100,9 @@ class AmqpRpcClient implements RpcClient {
       DefaultAddressBuilder<?> addressBuilder = Utils.addressBuilder();
       addressBuilder.queue(replyTo);
       String replyToAddress = addressBuilder.address();
+      // HTTP over AMQP 1.0 extension specification, 5.1:
+      // To associate a response with a request, the correlation-id value of the response properties
+      // MUST be set to the message-id value of the request properties.
       this.requestPostProcessor =
           (request, correlationId) -> request.replyTo(replyToAddress).messageId(correlationId);
     } else {

src/main/java/com/rabbitmq/client/amqp/impl/AmqpRpcServer.java

@@ -71,6 +71,9 @@ public Message message(byte[] body) {
           }
         };
     if (builder.correlationIdExtractor() == null) {
+      // HTTP over AMQP 1.0 extension specification, 5.1:
+      // To associate a response with a request, the correlation-id value of the response properties
+      // MUST be set to the message-id value of the request properties.
       this.correlationIdExtractor = Message::messageId;
     } else {
       this.correlationIdExtractor = builder.correlationIdExtractor();