support for catch all email address

Only by manually editing the postfix configuration trough the terminal 😟

I now do want to catch all email as it has become my lives work to report spam.

So I figured out an easier way to catch all email using simply the serveradmin command-line tool (this only takes email that would otherwise bounce):

sudo serveradmin settings mail:imap:lmtp_luser_relay_enabled = yes

sudo serveradmin settings mail:imap:lmtp_luser_relay = catchallusername

sudo postfix reload