Add docs for afterMarshal event.

Refs cakephp/cakephp#14383

Author: markstory

en/appendices/4-1-migration-guide.rst

@@ -70,7 +70,7 @@ ORM
 
 * BelongsToMany associations now respect the bindingKey set in the junction table's BelongsTo association.
   Previously, the target table's primary key was always used instead.
-  
+
 TestSuite
 ---------
 
@@ -120,6 +120,12 @@ Log
 * Log messages can now contain ``{foo}`` style placeholders. These placeholders
   will be replaced by values from the ``$context`` parameter if available.
 
+ORM
+---
+
+* The ORM now triggers an ``Model.afterMarshal`` event which is triggered after
+  each entity is marshaled from request data.
+
 TestSuite
 ---------
 

en/orm/saving-data.rst

@@ -636,6 +636,34 @@ Moreover, the data in ``beforeMarshal`` is a copy of the passed data. This is
 because it is important to preserve the original user input, as it may be used
 elsewhere.
 
+Modifying Entities After Updating From Request Data
+---------------------------------------------------
+
+The ``Model.afterMarshal`` event allows you to modify entities after they have
+been created or updated from request data. It can be useful to apply additional
+validation logic that you cannot easily express through Validator methods::
+
+    // Include use statements at the top of your file.
+    use Cake\Event\EventInterface;
+    use Cake\ORM\EntityInterface;
+    use ArrayObject;
+
+    // In a table or behavior class
+    public function afterMarshal(
+        EventInterface $event,
+        EntityInterface $entity,
+        ArrayObject $data,
+        ArrayObject $options
+    ) {
+        // Don't accept people who have a name starting with J on the 20th
+        // of each month.
+        if (substr($entity->name, 1) == 'J' && date('d') === 20) {
+            $entity->setError('name', 'No J people today sorry.');
+        }
+    }
+
+.. versionadded:: 4.1.0
+
 Validating Data Before Building Entities
 ----------------------------------------
 

en/orm/table-objects.rst

@@ -139,6 +139,7 @@ Event List
 
 * ``Model.initialize``
 * ``Model.beforeMarshal``
+* ``Model.afterMarshal``
 * ``Model.beforeFind``
 * ``Model.buildValidator``
 * ``Model.buildRules``
@@ -196,6 +197,17 @@ beforeMarshal
 The ``Model.beforeMarshal`` event is fired before request data is converted
 into entities. See the :ref:`before-marshal` documentation for more information.
 
+afterMarshal
+-------------
+
+.. php:method:: afterMarshal(EventInterface $event, EntityInterface $entity, ArrayObject $data, ArrayObject $options)
+
+The ``Model.afterMarshal`` event is fired after request data is converted
+into entities. Event handlers will get the converted entities, original request
+data and the options provided to the ``patchEntity()`` or ``newEntity()`` call.
+
+.. versionadded:: 4.1.0
+
 beforeFind
 ----------