Migrate away from app.php

[JonathanTreffler]

app.php is deprecated and will probably be removed in future Nextcloud releases.
This app uses app.php a lot. It would probably be a good idea to migrate before it has to be done under time pressure to reach compatibility with a release, which does not support app.php.

[pierreozoux]

Just got this message in logs:

[nextcloud][user_saml][0] {"reqId":"wYXZ7p0yorkeztvKM9sO","level":0,"time":"2023-09-25T12:59:30+00:00","remoteAddr":"","user":"--","app":"user_saml","method":"","url":"--","message":"/appinfo/app.php is deprecated, use \\OCP\\AppFramework\\Bootstrap\\IBootstrap on the application class instead.","userAgent":"--","version":"26.0.6.1","data":{"app":"user_saml"}}