Buster/Dovecot stats-writer

I noticed another issue on an upgraded test server...

postfix/pipe[9881]: 18F1A402DF: to=<drdev@example.com>, relay=dovecot, delay=0.05, delays=0/0.01/0/0.03, dsn=2.0.0, status=sent (delivered via dovecot service (lda(drdev@example.com,)Error: net_connect_unix(/var/run/dovecot/stats-writer) failed: Permission de))

By default the stats-writer socket is owned by root.dovecot ... while the delivery is running as the vmail user.

The solution from https://forum.iredmail.org/post67035.html#p67035 seems to work. It adds to dovecot.conf:

service stats {
    unix_listener stats-reader {
        user = vmail
        group = vmail
        mode = 0660
    }

    unix_listener stats-writer {
        user = vmail
        group = vmail
        mode = 0660
    }
}