nix_optimize: Add optimization of store and automatic GC call

modules/system/common.nix

@@ -23,6 +23,20 @@
     LC_TIME = "fr_FR.UTF-8";
   };
 
+  # Perform garbage collection weekly to maintain low disk usage
+  nix.gc = {
+    automatic = true;
+    dates = "*-*-* 20:00:00";
+    options = "--delete-older-than 1w";
+  };
+
+  # Optimize storage
+  # You can also manually optimize the store via:
+  #    nix-store --optimise
+  # Refer to the following link for more details:
+  # https://nixos.org/manual/nix/stable/command-ref/conf-file.html#conf-auto-optimise-store
+  nix.settings.auto-optimise-store = true;
+
   nixpkgs.config.allowUnfree = true;
 
   services.udev.packages = [ pkgs.yubikey-personalization ];