But now how can the public action methods of a "core" controller be overridden?
Now a lot of NonAction methods are marked as virtual, which it makes possible to override them if we inherit from the controller. But what about the public action methods? They are still no virtual, how can I override them?
In other words, what steps have to be done to inherit from a "core" controller like ShoppingCartController to implement/override the public actions in your own plugin?