Merge branch '5.4' into 6.3

* 5.4:
  Tweak
  [Messenger] Add `FlattenExceptionNormalizer`

Author: javiereguiluz

components/messenger.rst

@@ -161,6 +161,17 @@ Here are some important envelope stamps that are shipped with the Symfony Messen
 #. :class:`Symfony\\Component\\Messenger\\Stamp\\ErrorDetailsStamp`,
    an internal stamp when a message fails due to an exception in the handler.
 
+.. note::
+
+    The :class:`Symfony\\Component\\Messenger\\Stamp\\ErrorDetailsStamp` stamp
+    contains a :class:`Symfony\\Component\\ErrorHandler\\Exception\\FlattenException`,
+    which is a representation of the exception that made the message fail. You can
+    get this exception with the
+    :method:`Symfony\\Component\\Messenger\\Stamp\\ErrorDetailsStamp::getFlattenException`
+    method. This exception is normalized thanks to the
+    :class:`Symfony\\Component\\Messenger\\Transport\\Serialization\\Normalizer\\FlattenExceptionNormalizer`
+    which helps error reporting in the Messenger context.
+
 Instead of dealing directly with the messages in the middleware you receive the envelope.
 Hence you can inspect the envelope content and its stamps, or add any::