It is only a good thing to use for simple stateless daemons. It is
possible to use StateDirectory to store state, but it is extremely
limited. Notably, only service processes and root can correctly access
the state directory. This makes up for a bad practice to run maddyctl as
root what in turn screws up permissions on files in messages directory
when imap-* subcommands are used.
Migration note: Users of systemd unit with DynamicUser enabled should
move /var/lib/private/maddy to /var/lib/maddy before starting maddy
after update.
