Minidlna stores its database and thumbs at /var/cache/minidlna

Systemd on the other hand treats /var/cache/minidlna as a cache folder which wont survive service restarts and expects the directory to not exist when starting the service and CacheDirectory=minidlna exists in its service unit file.

the db_dir is supposed to be permanent.

Additional info:
* package version(s)
* config and/or log files etc.
* link to upstream bug report, if any

Steps to reproduce:
install minidlna and set it up. its cache dir is /var/cache/minidlna where it stores its db and thumbnails. This is expected to be readwrite and permanent (persists restarts of the service).

When starting after a reboot or restarting the service. it will fail with the following error:

Jul 01 16:15:25 emmet systemd[2222]: minidlna.service: Failed to set up special execution directory in /var/cache: File exists
Jul 01 16:15:25 emmet systemd[2222]: minidlna.service: Failed at step CACHE_DIRECTORY spawning /usr/bin/minidlnad: File exists

Clearing the variable Cachedirectory solves the problem.

From the documentation, the correct directory for semi-permanent data is /var/lib/ (StateDirectory) which would require minidlna.conf to define its db_dir to /var/lib/minidlna

Fix proposed:

changing db_dir to /var/lib/minidlna in minidlna.conf

adding an override for the systemd unit file minidlna.service with the following
[service]
ReadWritePaths=/var/lib/minidlna
CacheDirectory=
StateDirectory=minidlna

fixes the problem. The ReadWritePaths might be unnecessary.