[Serializer] Document support of PHP backed enumerations

Author: 94noni

components/serializer.rst

@@ -894,8 +894,14 @@ The Serializer component provides several built-in normalizers:
     string (``data:...``) such that files can be embedded into serialized data.
 
 :class:`Symfony\\Component\\Serializer\\Normalizer\\DateIntervalNormalizer`
-    This normalizer converts :phpclass:`DateInterval` objects into strings.
-    By default, it uses the ``P%yY%mM%dDT%hH%iM%sS`` format.
+    This normalizer converts a \BackedEnum objects into strings or integers.
+
+:class:`Symfony\\Component\\Serializer\\Normalizer\\BackedEnumNormalizer`
+    This normalizer converts a into strings.
+
+.. versionadded:: 5.4
+
+    The ``BackedEnumNormalizer`` was introduced in Symfony 5.4.
 
 :class:`Symfony\\Component\\Serializer\\Normalizer\\FormErrorNormalizer`
     This normalizer works with classes that implement

serializer.rst

@@ -80,6 +80,12 @@ As well as the following normalizers:
 * :class:`Symfony\\Component\\Serializer\\Normalizer\\ArrayDenormalizer`
 * :class:`Symfony\\Component\\Serializer\\Normalizer\\ConstraintViolationListNormalizer`
 * :class:`Symfony\\Component\\Serializer\\Normalizer\\ProblemNormalizer`
+* :class:`Symfony\\Component\\Serializer\\Normalizer\\BackedEnumNormalizer`
+
+.. versionadded:: 5.4
+
+    :class:`Symfony\\Component\\Serializer\\Normalizer\\BackedEnumNormalizer`
+    was introduced in Symfony 5.4.
 
 Other :ref:`built-in normalizers <component-serializer-normalizers>` and
 custom normalizers and/or encoders can also be loaded by tagging them as