flake-parts/setups/nixos: add foodogsquaredUtils to module args

An ugly solution but can't get around much for generating Nix modules with
the modularly set `foodogsquaredLib` so we'll have to make it evaluated before
the NixOS config evaluation.

lib/utils/nixos.nix

@@ -0,0 +1,33 @@
+{ lib }:
+
+{
+  # This is only used for home-manager users without a NixOS user counterpart.
+  mapHomeManagerUser = user: settings:
+    let
+      homeDirectory = "/home/${user}";
+      defaultUserConfig = {
+        extraGroups = lib.mkDefault [ "wheel" ];
+        createHome = lib.mkDefault true;
+        home = lib.mkDefault homeDirectory;
+        isNormalUser = lib.mkForce true;
+      };
+    in
+    ({ lib, ... }: {
+      home-manager.users."${user}" = { ... }: {
+        imports = [
+          {
+            home.username = user;
+            home.homeDirectory = homeDirectory;
+          }
+
+          ../../configs/home-manager/${user}
+        ];
+      };
+
+      users.users."${user}" = lib.mkMerge [
+        defaultUserConfig
+        settings
+      ];
+    });
+
+}

modules/flake-parts/setups/nixos.nix

@@ -28,6 +28,7 @@ let
     in
     (lib.makeOverridable nixosSystem) {
       specialArgs = {
+        foodogsquaredUtils = import ../../../lib/utils/nixos.nix { inherit lib; };
         foodogsquaredModulesPath = builtins.toString nixosModules;
       };
       modules = extraModules ++ [{