Merge branch '4.4' into 5.0

* 4.4:
  Remove AppBundle form path and namespace. refs #13178
  [Validator] Added the missing PHP format in a code example

Author: OskarStark

validation/custom_constraint.rst

@@ -240,3 +240,19 @@ not to the property:
         <class name="App\Entity\AcmeEntity">
             <constraint name="App\Validator\Constraints\ProtocolClass"/>
         </class>
+
+    .. code-block:: php
+
+        // src/Entity/AcmeEntity.php
+        use App\Validator\Constraints\ProtocolClass;
+        use Symfony\Component\Validator\Mapping\ClassMetadata;
+
+        class AcmeEntity
+        {
+            // ...
+
+            public static function loadValidatorMetadata(ClassMetadata $metadata)
+            {
+                $metadata->addConstraint(new ProtocolClass());
+            }
+        }