frontend sends it: a log holding non-ASCII characters ended with
"Server error occured". Fix #294, reported by @derdennis1012.
- [lmn_settings] [lmn_users] A refused request answers 403 instead of
failing with a 500. - [lmn_auth] [lmn_users] [lmn_session_new] Password errors stay
displayed until closed, so a long password policy message can be
read. - Schoolclasses and session members are sorted in natural order by
linuxmuster-tools (5a, 10b, then abitur). - [packaging] Depends on linuxmuster-tools7 (>= 7.4.19).