As the only consequence of isSystemUser is that if the uid is null then
it's allocated below 500, if a user has uid = something below 500 then
we don't require isSystemUser to be set.
Motivation: https://github.com/NixOS/nixpkgs/issues/112647
This is useful when the config doesn't entirely live in the Nix store,
but is configured to include mutable config files written at runtime.
Co-Authored-By: Puck Meerburg <puck@puck.moe>
When calling reload, bird attempts to reload the file that was given in
the command line. As the change of ${configFile} is never picked up,
bird will just reload the old file.
This way, the configuration is placed at a known location and updated.
