title.gettext deletion performed only by list owners, need authentication

is_owner([listname],[sender])  smtp,dkim      -> request_auth
is_listmaster([sender])        smtp,dkim       -> request_auth
is_owner([listname],[sender])  md5,smime -> do_it
is_listmaster([sender])        md5,smime -> do_it
true()                         smtp,dkim,md5,smime -> reject(reason='del_owner')
