Create generic Symfony controller able to display a legacy page && handle its display via the Symfony controller automatically

[fabienvallon]

Description

The legacy pages are rendered thanks to the Dispatcher from the index.php For now, the idea is to reverse what the legacy layout was. We need a LegacyController::legacyPageAction that would be used as a wrapper around the legacy controllers. In this controller the layout is rendered by Symfony and only the content at the center would be rendered by the legacy controller wrapped. The first step is to have this controller usable via a forced URL with the legacy controller passed as a parameter.

Like the generical Symfony layout is based on a Twig component, this legacy display should also be handled via a Twig component that will look like the generic one a lot except for a few exceptions that we need to anticipate (non-exhaustive list):

• the theme used should be the default one not the new-theme
• the loaded assets should match with the ones originally set via AdminController::setMedia(false)
• we need to handle correctly the backward compatibility, although it should already have been handled by Handle backward compatibility for smarty and context controller #33191
• ... there may be some other things to consider / think about

Once the generic controller is done and the controller is available we can then remove the principle based on RouteNotFoundException in the index.php file, any URL even the legacy ones would be handled via Symfony

Some generic route mapping will need to be found to catch the legacy URLs, the URL should not change to avoid breaking changes, it's just that the layout would now be handled by Symfony. This will simplify the work about authentication by Symfony a lot since after this ALL the pages (including the legacy ones) would be handled by the framework.

Example:

legacy_controller_route:
  path: /controller={controllerName}
  defaults:
    _controller: LegacyLayoutController::legacyPageAction

Acceptance test

1. This controller should be able to display a legacy page ( TBD )
   Could be test manually by forcing the URL

2. Handle legacy page display via the Symfony controller automatically and systematically

3. UI tests work fine with Symfony layout enabled, and on legacy pages

4. Test multistore shop list

5. Test the productcomment in the BO. It should work as ISO