minor #12154 [Messenger] Information about why consumers do not show up in the (rabbitmq) admin panel (smoench)

This PR was merged into the 4.3 branch.

Discussion
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[Messenger] Information about why consumers do not show up in the (rabbitmq) admin panel

I wondered why the consumers were not shown up in the rabbitmq admin panel. I found following explanation symfony/symfony#30259 (comment) from @chalasr which should be documented.
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Commits
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27339f2 [Messenger] Information about why consumers do not show up in the (rabbimq) admin panel

Author: OskarStark

messenger.rst

@@ -759,6 +759,17 @@ your Envelope::
         new AmqpStamp('custom-routing-key', AMQP_NOPARAM, $attributes)
     ]);
 
+.. caution::
+
+    The consumers do not show up in an admin panel as this transport does not rely on
+    ``\AmqpQueue::consume()`` which is blocking. Having a blocking receiver makes
+    the ``--time-limit/--memory-limit`` options of the ``messenger:consume`` command as well as
+    the ``messenger:stop-workers`` command inefficient, as they all rely on the fact that
+    the receiver returns immediately no matter if it finds a message or not. The consume
+    worker is responsible for iterating until it receives a message to handle and/or until one
+    of the stop conditions is reached. Thus, the worker's stop logic cannot be reached if it
+    is stuck in a blocking call.
+
 Doctrine Transport
 ~~~~~~~~~~~~~~~~~~