fix(isLegitimatedForUserId): Setup mountpoints to check file access

[mejo-]

This fixes workflows on groupfolders, as it will consider access to files in groupfolders.

It also fixes false positives where access to files was limited by other means not taken into account before, e.g. access control.

For postDelete events, check for permissions of the parent folder instead, as the file itself no longer exists.

Fixes: nextcloud/flow_notifications#71

Idea taken from #38946

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Backports requested where applicable (ex: critical bugfixes)

[blizzz]

@icewind1991 do you think this can be a performance killer?

[icewind1991]

@icewind1991 do you think this can be a performance killer?

It isn't worse than the previous code (getAccessList is probably just as bad), but if this gets called in a loop (like for every file in a folder that is being accessed) than performance will be dead yes.
I do not know enough about workflow to know how this code is called

[mejo-]

Cypress test failures seem unrelated. PR should be ready for review 😊

[mejo-]

By the way, I manually tested the following scenarios (all with a flow_notification flow defined by admin for files with a system tag):

• User jane creates/changes a file in a tagged folder shared with her by admin -> isLegitimatedForUserId returns true
• User jane deletes a file in a tagged folder shared with her by admin -> isLegitimatedForUserId returns true
• User jane creates/changes a file in a tagged groupfolder where admin has access -> isLegitimatedForUserId returns true
• User jane deletes a file in a tagged groupfolder where admin has access -> -> isLegitimatedForUserId returns true
• User jane creates/changes a file in a tagged groupfolder where admin doesn't have access -> isLegitimatedForUserId returns false
• User jane deletes a file in a tagged groupfolder where admin doesn't have access -> -> isLegitimatedForUserId returns false

[juliusknorr]

One psalm complaint, but otherwise seems reasonable 👍

[mejo-]

Thanks @juliushaertl. I addressed the psalm complaint now.

[mejo-]

Will need manual backports without the public interface changes to stable27 and stable26.

[mejo-]

/backport to stable27

[mejo-]

/backport to stable27