remove "final" keyword from classes and make properties protected

[alyamovsky]

hi! thanks for the great bundle

can you remove the "final" keyword from classes, especially from controllers? since code from a bundle should be customizable, it would be nice to be able to add some apidoc annotations for example

[spideyfusion]

Could you provide us with a couple of extension use cases so we can get a better idea on what you're trying to achieve? Certain classes are marked as final because they weren't designed with extending in mind.

[alyamovsky]

of course, two first cases that coming to mind are:

1. to add some nelmio/apidoc annotations for controllers since our frontend devs will be using it
2. to set some decorator for the phpleague/oauth AuthorizationServer to be able to set the PKCE challenge for the auth code flow.