feat: add guix as a daemon service

modules/nixos/desktop/default.nix

@@ -1,10 +1,3 @@
-{
-  imports = [
-    ./fonts.nix
-    ./graphic.nix
-    ./misc.nix
-    ./peripherals.nix
-    ./security.nix
-    ./visualisation.nix
-  ];
+{mylib, ...}: {
+  imports = mylib.scanPaths ./.;
 }

modules/nixos/desktop/guix.nix

@@ -0,0 +1,21 @@
+{
+  # https://github.com/NixOS/nixpkgs/blob/master/nixos/modules/services/misc/guix/default.nix
+  services.guix = {
+    enable = true;
+    # The store directory where the Guix service will serve to/from.
+    # NOTE: most of the cached builds are assumed to be in `/gnu/store`.
+    storeDir = "/gnu/store";
+    # The state directory where Guix service will store its data such as its
+    # user-specific profiles, cache, and state files.
+    stateDir = "/var";
+    gc = {
+      enable = true;
+      # https://guix.gnu.org/en/manual/en/html_node/Invoking-guix-gc.html
+      extraArgs = [
+          "--delete-generations=1m"
+          "--free-space=10G"
+          "--optimize"
+        ];
+    };
+  };
+}