nix: extract nix config

system/nix.nix

@@ -0,0 +1,33 @@
+{ config, pkgs, inputs, ... }: {
+  # Allow unfree packages
+  nixpkgs.config.allowUnfree = true;
+
+  nix.registry.nixpkgs.flake = inputs.nixpkgs;
+  nix = {
+    gc = {
+      automatic = true;
+      dates = "weekly";
+      options = "--delete-older-than 7d";
+    };
+    optimise.automatic = true;
+    settings = {
+      auto-optimise-store = true;
+      substituters = [
+        # "http://nixcache.lelgenio.1337.cx:5000"
+        "https://hyprland.cachix.org"
+        "https://lelgenio.cachix.org"
+        "https://wegank.cachix.org"
+      ];
+      trusted-public-keys = [
+        # "nixcache.lelgenio.1337.cx:zxCfx7S658llDgAUG0JVyNrlAdFVvPniSdDOkvfTPS8="
+        "hyprland.cachix.org-1:a7pgxzMz7+chwVL3/pzj6jIBMioiJM7ypFP8PwtkuGc="
+        "lelgenio.cachix.org-1:W8tMlmDFLU/V+6DlChXjekxoHZpjgVHZpmusC4cueBc="
+        "wegank.cachix.org-1:xHignps7GtkPP/gYK5LvA/6UFyz98+sgaxBSy7qK0Vs="
+      ];
+    };
+    package = pkgs.unstable.nixFlakes; # or versioned attributes like nixVersions.nix_2_8
+    extraOptions = ''
+      experimental-features = nix-command flakes
+    '';
+  };
+}