[Messenger] Allow to define batch size when using BatchHandlerTrait with getBatchSize()

Author: alexandre-daubois

messenger.rst

@@ -2173,14 +2173,26 @@ provided in order to ease the declaration of these special handlers::
             }
         }
 
-        // Optionally, you can redefine the `shouldFlush()` method
-        // of the trait to define your own batch size
+        // Optionally, you can either redefine the `shouldFlush()` method
+        // of the trait to define your own batch size...
         private function shouldFlush(): bool
         {
             return 100 <= \count($this->jobs);
         }
+
+        // ... or redefine the `getBatchSize()` method if the default
+        // flush behavior suits your needs
+        private function getBatchSize(): int
+        {
+            return 100;
+        }
     }
 
+.. versionadded:: 6.3
+
+    The :method:`Symfony\\Component\\Messenger\\Handler\\BatchHandlerTrait::getBatchSize`
+    method was introduced 6.3.
+
 .. note::
 
     When the ``$ack`` argument of ``__invoke()`` is ``null``, the message is