chore: fix api test conventions
chore: rubocop -A spec/
chore: more rubocop -A
fix failing test
rubocop fixes
removes helper methods that are in my opinion dead code
more rubocop fixes
rubocop -a --auto-gen-config
Messagegroups are a new kind of group. Every user can join and leave such a
group on her own. They are useful to create topics for mails.
E.g. if there is a weekly newsletter we can create a new messagegroup for
it and every user which is interested in receiving the newsletter can join
the corresponding group.
