Couple of changes:
- move home to /var/lib/ddclient so we can enable ProtectSystem=full
- do not stick binary into systemPackages as it will only run as a daemon
- run as dedicated user/group
- document why we cannot run as type=forking (output is swallowed)
- secure things by running with ProtectSystem and PrivateTmp
- .pid file goes into /run/ddclient
- let nix create the home directory instead of handling it manually
- make the interval configurable
4ce76d9e1a