fixes
'system' has been renamed to/replaced by 'stdenv.hostPlatform.system'
Wherever possible, it's best to reference the hostPlatform of the
nixpkgs instance directly via `config`. This is only possible in NixOS
systems though, for standalon home-manager configs we need to get that
value through `pkgs.stdenv`.
Introduce a guest user module that sets up a guest user with the default
desktop home packages through the home-manager NixOS module.
Enabled on thinknix.
