On my PC, there are several usual users that can logon to it. To watch movies, there should be one special user (which may be even passwordless) that can only run Kodi. I am thinking about a setup where it does not run any Window Manager (like Cinnamon), but Kodi is directly run by LightDM. Running Kodi as WM is already possible for any user, but this special user should not be able to choose another Window Manager - like Cinnamon. How do I setup such a user?