Clarify goals of AbstractController

[fabpot]

Q	A
Branch?	5.4
Bug fix?	no
New feature?	no
Deprecations?	yes
Tickets	Refs #42418
License	MIT
Doc PR	n/a

AbstractController should only be about HTTP-related features and we should not encourage developers to put some other logic in controllers. See #42418 for a discussion about it.

[OskarStark]

Make sense 👍

[ro0NL]

i'll assume the local service refs (eg. getSubscribedServices) remain available in a protected container like till forever :)

UPGRADE file should be updated :')

[wouterj]

Makes sense, although getDoctrine() has been there for so long that we have to update quite some docs I think. Also a friendly ping to @weaverryan as I think this will impact SymfonyCasts as well.

[zairigimad]

Makes sense, but Messenger is one of the recently added components in the AbstractControllers, I believe it's not only HTTP related feature, should this part be flagged as deprecated and moved out from the AbstractController?

[chalasr]

I suggest to trigger a deprecation notice from AbstractController::get() when the passed id is one of message_bus, messenger.default_bus or doctrine.

[jderusse]

👍 for cleaning this class

[fabpot]

I suggest to trigger a deprecation notice from AbstractController::get() when the passed id is one of message_bus, messenger.default_bus or doctrine.

I will deprecate get and has in another PR as I don't think these methods make sense as they give access to a limited (and arbitrary?) set of services.

[fabpot]

Follow-up: #42442