Switch to snowfall flake configuration

modules/nix/default.nix

@@ -0,0 +1,53 @@
+{ options, config, pkgs, lib, ... }:
+
+with lib;
+#with lib.internal;
+let cfg = config.custom.nix;
+in
+{
+  options.custom.nix = with types; {
+    enable = mkBoolOpt true "Whether or not to manage nix configuration.";
+    package = mkOpt package pkgs.nix "Which nix package to use.";
+  };
+
+  config = mkIf cfg.enable {
+    environment.systemPackages = with pkgs; [
+      deploy-rs
+      nixfmt
+      nix-index
+      nix-prefetch-git
+      nixpkgs-review
+      nurl
+      nix-init
+    ];
+
+    nix = {
+      package = cfg.package;
+      settings = {
+        substituters = [
+          "https://cache.nixos.org/"
+          "https://nix-community.cachix.org"
+          "https://prismlauncher.cachix.org"
+        ];
+        trusted-public-keys = [
+          "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY="
+          "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
+          "prismlauncher.cachix.org-1:GhJfjdP1RFKtFSH3gXTIQCvZwsb2cioisOf91y/bK0w="
+        ];
+        trusted-users = [ "root" ];
+        sandbox = true;
+        require-sigs = true;
+        max-jobs = "auto";
+        auto-optimise-store = true;
+        allowed-users = [ "*" ];
+        experimental-features = [ "nix-command" "flakes" ];
+        warn-dirty = false;
+      };
+
+      # flake-utils-plus
+      generateRegistryFromInputs = true;
+      generateNixPathFromInputs = true;
+      linkInputs = true;
+    };
+  };
+}