Dear Maintainer,

since the last update a fresh rpki-client installation will create
/var/lib/rpki-client/cache with the wrong permissions. It should be
owned by _rpki-client:_rpki_client but is installed as root:root.

As a result rpki-client will fail to run on fresh installations unless
one runs chown -R _rpki-client:_rpki-client /var/lib/rpki-client/cache

This can be fixed by adding /var/lib/rpki-client/cache to d/rpki-client.tmpfiles.
I will submit the fix seperately via salsa.

Salsa won't let me open a merge request so I will attach the fix as a patch file here.