fix(OCS): Add IRequest::getFormat to determine the response Content-Type the same way everywhere

[provokateurin]

The OCSMiddleware handles the ?format=json query parameter and Accept: application/json request header, but ocs/v1.php uses ApiHelper::respond which only handles ?format=json so far.

[nickvergessen]

While a good and nice fix, I fear this could break current clients working around the problem since years. So I'd suggest to delay it until after the branch off?

[provokateurin]

this could break current clients working around the problem since years

So the issue is known and was manually handled by some clients? 🙈

I'm fine with waiting, I just found this while fuzzing the API and it has been broken this way since forever, so fixing it is not that urgent.

[come-nc]

It would make sense to add a method to IRequest to get requested format, maybe?

[provokateurin]

I have too many questions about the code I saw 🙈

[nickvergessen]

Should have upstreamed https://github.com/nextcloud/spreed/blob/38e56a3fe460f07e128c49be2759362592728a22/lib/Controller/AEnvironmentAwareOCSController.php#L60-L75 before it was cool :D

[nickvergessen]

Opposed to Controller::getResponderByHTTPHeader() which was used before, this here no longer checks if there is a responder registered and does not fall back to the default type correctly.
E.g. When you create a share for a file that can not have a preview (e.g. PDF without PDF being enabled), instead of having a proper 404, the response now is:

Technische Details

    Entfernte Adresse: ::1
    Anfragekennung: 3RuRvo3TEr52XxYi3pq6
    Typ: DomainException
    Code: 0
    Nachricht: No responder registered for format xhtml+xml!
    Datei: /home/nickv/Nextcloud/33/server/lib/public/AppFramework/Controller.php
    Zeile: 139


Trace

#0 /home/nickv/Nextcloud/33/server/lib/private/AppFramework/Http/Dispatcher.php(227): OCP\AppFramework\Controller->buildResponse(Object(OCP\AppFramework\Http\DataResponse), '...')
#1 /home/nickv/Nextcloud/33/server/lib/private/AppFramework/Http/Dispatcher.php(118): OC\AppFramework\Http\Dispatcher->executeController(Object(OCA\Files_Sharing\Controller\PublicPreviewController), '...')
#2 /home/nickv/Nextcloud/33/server/lib/private/AppFramework/App.php(153): OC\AppFramework\Http\Dispatcher->dispatch(Object(OCA\Files_Sharing\Controller\PublicPreviewController), '...')
#3 /home/nickv/Nextcloud/33/server/lib/private/Route/Router.php(321): OC\AppFramework\App::main('...', '...', Object(OC\AppFramework\DependencyInjection\DIContainer), Array)
#4 /home/nickv/Nextcloud/33/server/lib/base.php(1096): OC\Route\Router->match('...')
#5 /home/nickv/Nextcloud/33/server/index.php(25): OC::handleRequest()
#6 {main}

This works properly until Nextcloud 31.

[provokateurin]

#55620