[admin] prevent users joining groups with high permissions
[admin] prevent users joining groups with high permissions

This is a sort-of safety check that should prevent bad situations where
somehow a group role gets a administrator permission flipped on, which
can give users too much access. Obviously this doesn't protect against
users already having the role, but that will come w/ locked roles.

ThaTiemsz/jetski,aliasfalse/rowboat,ThaTiemsz/jetski,b1naryth1ef/rowboat,b1naryth1ef/rowboat,b1naryth1ef/rowboat,aliasfalse/rowboat,b1naryth1ef/rowboat,ThaTiemsz/jetski,ThaTiemsz/jetski,aliasfalse/rowboat,aliasfalse/rowboat