The web application routers were removed in the 4.0 branch in favor of using the Framework's Router package. 1.x of this package requires a Joomla\Controller\ControllerInterface implementation, of which it is impossible to do with existing CMS code. This PR therefore makes the "no MVC" controller base class and interface compatible with the Framework's Controller package.
Testing Instructions
Code review
Documentation Changes Required
The $app and $input properties will now be private, requiring the use of the appropriate getters to retrieve this objects in subclasses.
joomla-cms-bot
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We need to test com_config to merge this - and just make sure that all still works as expected as that all runs on new mvc