Optional controller for every widget which has its own logic, e.g. in forms.

It always handles a single widget, usually passed in as a database
identifier through the controller URL. Needs to be constructed as a nested
controller within a .
## Forms
You can add forms like in any other SilverStripe controller. If you need
access to the widget from within a form, you can use
`$this->controller->getWidget()` inside the form logic.
Note: Widget controllers currently only work on objects,
because the logic is implemented in .
Copy this logic and the URL rules to enable it for other controllers.