show mailbox quota by IMAP GETROOTQUOTA
Various mail clients request the quota for the mailbox in order to display it.
However, the value is not correct and causes irritation among users.
The Dovecot quota plugin implementation returns for a IMAP GETROOTQUOTA request a wrong value. It shows the user quota of the / partition filesystem.
It would be better if the real quota value for the mailbox was returned, as doveadm also shows it.