docs: add documentation for extra formatter options

docs/_partials/fields/formatter-callable.rst

@@ -7,11 +7,13 @@ Formatting with a Callable
 
 The most immediate way of formatting a field is by passing a callable function
 or object to the ``formatter`` option. Callable functions or objects will
-receive 3 arguments:
+receive 5 arguments:
 
 * ``$name`` The name of the field to be displayed
 * ``$value`` The value of the field that should be outputted
 * ``$entity`` The entity object from which the field was extracted
+* ``$options`` An array of options passed to the CrudView helper when the field is being processed
+* ``$View`` The view object in use during formatting
 
 For example, imagine that when displaying the ``published_time`` property, we
 wanted to also display who approved the article:
@@ -42,3 +44,17 @@ only configure the settings for one or two.
             }
         ],
     ]);
+
+In some cases, it may be useful to access a helper within the callable. For instance, you might want to create a link:
+
+.. code-block:: php
+
+    $action = $this->Crud->action();
+    $action->config('scaffold.fields', [
+        'title',
+        'external_id' => [
+            'formatter' => function ($name, $value, $entity, $options, $View) {
+                return $View->Html->link($name, sprintf('https://example.com/view/%d', $value));
+            }
+        ],
+    ]);