Add doc for Yaml's option configClass.

Author: WedgeSama

reference/constraints/Yaml.rst

@@ -145,6 +145,69 @@ Parameter        Description
 ``{{ line }}``   The line where the YAML syntax error happened
 ===============  ==============================================================
 
+``configClass``
+~~~~~~~~~~~
+
+**type**: ``string`` **default**: ``null``
+
+This option enable a validation check using a class that implement
+:class:`Symfony\Component\Config\Definition\ConfigurationInterface`. You need to give it the full classname of your
+configuration class.
+
+.. configuration-block::
+
+    .. code-block:: php-attributes
+
+        // src/Entity/Report.php
+        namespace App\Entity;
+
+        use App\Yaml\MyConfiguration;
+        use Symfony\Component\Validator\Constraints as Assert;
+
+        class Report
+        {
+            #[Assert\Yaml(
+                configClass: MyConfiguration::class,
+            )]
+            private string $customConfiguration;
+        }
+
+    .. code-block:: php
+
+        // src/Entity/Report.php
+        namespace App\Entity;
+
+        use App\Yaml\MyConfiguration;
+        use Symfony\Component\Validator\Constraints as Assert;
+        use Symfony\Component\Validator\Mapping\ClassMetadata;
+
+        class Report
+        {
+            public static function loadValidatorMetadata(ClassMetadata $metadata): void
+            {
+                $metadata->addPropertyConstraint('customConfiguration', new Assert\Yaml([
+                    'configClass' => MyConfiguration::class,
+                ]));
+            }
+        }
+
+For more info about Configuration, see :doc:`Config component </components/config>`.
+
+``configMessage``
+~~~~~~~~~~~
+
+**type**: ``string`` **default**: ``This value do not match the required config.``
+
+This message shown if the given YAML value is invalid regarding the Configuration class.
+
+You can use the following parameters in this message:
+
+===============  ==============================================================
+Parameter        Description
+===============  ==============================================================
+``{{ error }}``  The full error message from the config Processor
+===============  ==============================================================
+
 .. include:: /reference/constraints/_groups-option.rst.inc
 
 .. include:: /reference/constraints/_payload-option.rst.inc