auth module logging

[AP]

Hi,

As per my discussion with cmouse on irc, I'm currently just using
dovecot for its auth mechanism, etc capabilities (alas, Exim does
not support argon directly). Tis a fun little side project. :)

I have the config pared down as far as I think is reasonable (see
below) and all is working well except that dovecot is very silent.

Errors hit the logs but I would appreciate seeing successful auths
happen for the additional piece of mind. Cmouse and I couldn't
find a way to do it on irc and it appears that the capability is
missing. Successul /logins/ can be logged but auths, by themselves,
cannot.

I would appreciate if the ability was added.

Dovecot 2.3.7.1 is in use.

Thanks

# Pigeonhole version 0.5.7.1 (db5c74be)
# OS: Linux 5.2.4 x86_64 Debian 10.0
# Hostname: bob
auth_mechanisms = plain login
auth_verbose = yes
auth_verbose_passwords = sha1:16
log_timestamp = "%Y-%m-%d %H:%M:%S %z "
mail_log_prefix = "%{pid}<%{session}> %{service}(%{user}): "
passdb {
  args = /etc/dovecot/dovecot-sql.conf.ext
  driver = sql
}
service anvil {
  unix_listener anvil-auth-penalty {
    mode = 00
  }
}
service auth-worker {
  user = $default_internal_user
}
service auth {
  unix_listener auth-client {
    group = Debian-exim
    mode = 0660
  }
}
ssl = no
userdb {
  args = /etc/dovecot/dovecot-sql.conf.ext
  driver = sql
}

AP