This patch improves the overall security assessment score given by
`systemd-analyze security rest-server.service` from "1.3 OK" to "0.6 SAFE"
(when using systemd-analyze version 253)
* Remove `AF_INET AF_INET6` from RestrictAddressFamilies.
Sockets originating from socket activation are not affected by the
systemd directive RestrictAddressFamilies.
See systemd.exec man page.
* Add `PrivateNetwork=yes`
as recommended for socket-activated services in the systemd.socket man page
* Add dependency on rest-server.socket
Signed-off-by: Erik Sjölund <erik.sjolund@gmail.com>
