I didn't realize `network.target` is very ambiguous. The next best thing
for booting up the service after the system is up is `default.target`
but we're being explicit here for NixOS services just to make sure.
It was supposed to create the directory if it wasn't found which is
self-defeating. In any case, it will still fail if the directory is in
the way of an unmounted device.
There is the `--paths` option for that purpose. It also eliminates the
workaround for creating the directory before starting the service for
newly-bootstrapped systems.
The several hardening options have also been corrected.
Structure-wise, it is pretty similar to the gallery-dl service. It was
about to be combined into a bigger service module as a dedicated service
for multimedia archiving but it is better to have them modularized in
the long run.
