Move nix code under nix/

nix/lib.nix

@@ -0,0 +1,34 @@
+{ nixpkgs }:
+let
+  inherit (nixpkgs) lib;
+in
+{
+  makeServiceConfig = { system, module }:
+    let
+      pkgs = nixpkgs.legacyPackages.${system};
+
+      nixosConfig = lib.nixosSystem {
+        inherit system;
+        specialArgs = { };
+        modules = [ module ];
+      };
+      services = lib.flip lib.genAttrs
+        (serviceName:
+          nixosConfig.config.systemd.units."${serviceName}.service".unit)
+        nixosConfig.config.service-manager.services;
+
+      servicesPath =
+        pkgs.writeTextFile {
+          name = "services";
+          destination = "/services.json";
+          text = lib.generators.toJSON { } services;
+        };
+      activationScript = pkgs.writeShellScript "activate" ''
+        echo "${servicesPath}"
+      '';
+    in
+    pkgs.linkFarmFromDrvs "service-manager" [
+      servicesPath
+      activationScript
+    ];
+}