Improve ease of extention

In our usage we need to extend the ControllerInvoker to have responses normalised from a generic Payload into a standard Response.

To make this easier it would be helpful if some private methods were instead protected and the Invoker fetching the default resolver chain were separated out from the creation of the ControllerInvoker.

Fixes #105

You can see our proposed implementation of the ControllerInvoker here. With the proposed patch here, that would be vastly simplified and easier to maintain, something like:

    #[\Override]
    protected function processResponse($response) {
        return \core\di::get(response_handler::class)->standardise_response($response);
    }

Likewise our custom Bridge implementation would be vastly simplified by breaking apart the Bridge::createControllerInvoker method from this, to:

class bridge extends \DI\Bridge\Slim\Bridge {
    #[\Override]
    protected static function createControllerInvoker(ContainerInterface $container): ControllerInvoker {
        return new controller_invoker(self::createInvoker($container));
    }
}

PHP-DI / Slim-Bridge

Improve ease of extention #89