fix(ACL): Add check to prevent users from revoking their own access

[icewind1991]

When changing ACL rules, check if the new rule set would lead the current user without read permissions

• make the UI properly handle the error
• (maybe) add an option to force revoking the access anyway

[jancborchardt]

@icewind1991 since you said

Would it maybe make more sense to just fully prevent users from revoking their own access?

I would say the modal is better, because maybe you do want to get out of the group folder?

Access removal
Proceeding will remove your own access to this group folder.
[ Cancel ] [ Remove own access ]

[provokateurin]

Fixes #2822

[provokateurin]

I would say the modal is better, because maybe you do want to get out of the group folder?

I don't think this makes sense, since in fact you do not remove yourself from the Team folder this way.
If the user no longer wants access, then an admin has to remove their access and they can not do it themselves through ACL (which also only works on sub folders, not the root Team folder itself anyway).

[provokateurin]

/backport to stable31