minor #16885 [Messenger] Add an info about redeliver_timeout (doctrine) (axi)

This PR was squashed before being merged into the 5.4 branch.

Discussion
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[Messenger] Add an info about redeliver_timeout (doctrine)

Had the case with a multi hour job :-) Took me a while, maybe that can help somebody reading the doc

Commits
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534e587 [Messenger] Add an info about redeliver_timeout (doctrine)

Author: javiereguiluz

messenger.rst

@@ -1361,6 +1361,11 @@ auto_setup          Whether the table should be created
                     automatically during send / get.       true
 ==================  =====================================  ======================
 
+
+.. note::
+
+    ``redeliver_timeout`` must be set to a greater value than your slowest message duration. Failing to do so will result in messages being started a second time while the first one is still running.
+
 .. versionadded:: 5.1
 
     The ability to leverage PostgreSQL's LISTEN/NOTIFY was introduced