Roles select must be limited to disallow permission increases

[PVince81]

Steps

1. Create three users "Alice", "Bob" and "Charlie"
2. Login as "Alice"
3. Create a folder "test"
4. Share "test" with "Bob" with the "Viewer" role, and allow re-sharing
5. Login as "Bob"
6. Share "test" with "Charlie" with "Editor" permissions

Expected result

The roles dropdown should not allow selecting anything else than "Viewer".
Maybe if there's only a single entry, don't even show the dropdown and keep a single entry.
Maybe grey out the other entries in the dropdown so we know they exist but cannot be selected.

Actual result

All entries are visible and can be selected.
Saving will leave the dialog with an error "Cannot set the requested share permissions for test".

Side note: when catching such error in general, the "add collaborator" dialog must not disappear!

Version

v0.3.0

@kulmann FYI as we observed this during our recent work.

cc @pmaier1

[kulmann]

Wait with implementation until #6039 is merged

[AlexAndBear]

Resharing seems not to be allowed anymore, so is this still an issue?

[pascalwengerter]

Resharing seems not to be allowed anymore, so is this still an issue?

Yes, resharing is part of the roadmap (ideally this week in oCIS)