feat: nix-darwin-kickstarter minimal

modules/nix-core.nix

@@ -1,20 +1,22 @@
-{ pkgs, ... }:
-
+{ pkgs, lib, ... }:
 {
-  nix.settings = {
-    # enable flakes globally
-    experimental-features = ["nix-command" "flakes"];
+  nix = {
+    enable = true;
+    package = pkgs.nix;
+
+    settings = {
+      experimental-features = [ "nix-command" "flakes" ];
+      substituters = [ "https://nix-community.cachix.org" ];
+      trusted-public-keys = [
+        "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
+      ];
+      builders-user-substitutes = true;
+      auto-optimise-store = false;  # issue https://github.com/NixOS/nix/issues/7273
+    };
   };
 
-  # Allow unfree packages
-  nixpkgs.config = {
-    allowUnfree = true;
-    allowBroken = true;
+  gc = {
+    automatic = lib.mkDefault true;
+    options = lib.mkDefault "--delete-older-than 7d";
   };
-
-  # Auto upgrade nix package and the daemon service.
-  nix.package = pkgs.nix;
-
-  # Enable Determinate
-  nix.enable = false;
 }