[python lino_noi.lib.users] currently extends [python lino_xl.lib.online.users], but that's probably not needed, and it causes each database lookup to hit two tables instead of one. e.g. faculties.end_user_model must become users.User instead of contacts.Partner. This might be a reason for #2044. ​Before doing this change, I would like to have a way for measuring the gain in performance.