minor #17979 [Serializer] Add feature description for AbstractNormalizer::REQUIRE_ALL_PROPERTIES context option (Christian Kolb, christian-kolb)

This PR was merged into the 6.3 branch.

Discussion
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[Serializer] Add feature description for `AbstractNormalizer::REQUIRE_ALL_PROPERTIES` context option

This PR adds the feature description for the new context flag for the Serializer component introduced here: symfony/symfony#49553

Commits
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71a4ef4 Rename context flag
ea5c341 Update components/serializer.rst
3b24418 Update components/serializer.rst
e1f5d7c Update components/serializer.rst
b665eeb Update components/serializer.rst
0b49d9b Fix broken code example
1b0e274 Add feature description

Author: xabbuh

components/serializer.rst

@@ -1255,6 +1255,33 @@ to ``true``::
     $result = $normalizer->normalize($dummy, 'json', [AbstractObjectNormalizer::SKIP_NULL_VALUES => true]);
     // ['bar' => 'notNull']
 
+Require all Properties
+----------------------
+
+By default, the Serializer will add ``null`` to nullable properties when the parameters for those are not provided.
+You can change this behavior by setting the ``AbstractNormalizer::REQUIRE_ALL_PROPERTIES`` context option
+to ``true``::
+
+    class Dummy
+    {
+        public function __construct(
+            public string $foo,
+            public ?string $bar,
+        ) {
+        }
+    }
+
+    $data = ['foo' => 'notNull'];
+
+    $normalizer = new ObjectNormalizer();
+    $result = $normalizer->denormalize($data, Dummy::class, 'json', [AbstractNormalizer::REQUIRE_ALL_PROPERTIES => true]);
+    // throws Symfony\Component\Serializer\Exception\MissingConstructorArgumentException
+
+.. versionadded:: 6.3
+
+    The ``AbstractNormalizer::PREVENT_NULLABLE_FALLBACK`` context option
+    was introduced in Symfony 6.3.
+
 Skipping Uninitialized Properties
 ---------------------------------