Merge branch '5.4' into 6.0

* 5.4:
  [Serializer] Add documentation about context and Serializer::EMPTY_ARRAY_AS_OBJECT

Author: javiereguiluz

serializer.rst

@@ -144,6 +144,33 @@ properties and setters (``setXxx()``) to change properties:
             ;
         };
 
+Serializer Context
+------------------
+
+The serializer can define a context to control how the (de)serialization of
+resources. This context is passed to all normalizers. For example:
+
+* :class:`Symfony\\Component\\Serializer\\Normalizer\\DateTimeNormalizer` uses
+  ``datetime_format`` key as date time format;
+* :class:`Symfony\\Component\\Serializer\\Normalizer\\AbstractObjectNormalizer`
+  uses ``empty_iterable_as_object`` to represent empty objects as ``{}`` instead
+  of ``[]`` in JSON.
+
+.. versionadded:: 5.4
+
+    The usage of the ``empty_arrays_as_object`` option by default in the
+    Serializer was introduced in Symfony 5.4.
+
+You can pass the context like following::
+
+    $serializer->serialize($something, 'json', [
+        DateTimeNormalizer::FORMAT_KEY => 'Y-m-d H:i:s',
+    ]);
+
+    $serializer->deserialize($someJson, Something::class, 'json', [
+        DateTimeNormalizer::FORMAT_KEY => 'Y-m-d H:i:s',
+    ]);
+
 .. _serializer-using-serialization-groups-annotations:
 
 Using Serialization Groups Annotations