split base system config into a module

modules/system/base.nix

@@ -0,0 +1,20 @@
+{ config, inputs, modules, overlays, ... }: {
+  system = {
+    configurationRevision = inputs.self.rev;
+    nixos = rec {
+      version = config.system.nixos.release + versionSuffix;
+      versionSuffix = "-${config.system.name}.r${builtins.toString inputs.self.revCount}.${inputs.self.shortRev}";
+    };
+  };
+  nix.registry.nixpkgs.flake = inputs.nixpkgs;
+  nixpkgs.overlays = overlays;
+
+  home-manager = {
+    useGlobalPkgs = true;
+    useUserPackages = true;
+    extraSpecialArgs = {
+      inherit inputs modules;
+      enableGUI = true;
+    };
+  };
+}