Makes it easier to configure `rust-motd`. Currently, it takes care of
the following things:
* Creating a timer to regularly refresh the `motd`-text and a hardened
service (which is still root to get access to e.g. fs-mounts, but
read-only because of hardening flags).
* Disabling `PrintLastLog` in `sshd.conf` if the last-login feature of
`rust-motd` is supposed to be used.
* Ensure that the banner is actually shown when connecting via `ssh(1)`
to a remote server with this being enabled.
