🚧 Update user configuration loading and use formatter

modules/nixos/system/grub/default.nix

@@ -0,0 +1,35 @@
+{
+  lib,
+  self,
+  config,
+  ...
+}: let
+  inherit (lib) mkEnableOption mkIf;
+  inherit (self) namespace;
+
+  cfg = config.${namespace}.system.grub;
+in {
+  options.${namespace}.system.grub = {
+    enable = mkEnableOption "the grub bootloader.";
+  };
+
+  config = mkIf cfg.enable {
+    boot.loader.systemd-boot.enable = false;
+
+    boot.loader.grub = {
+      enable = true;
+      devices = ["nodev"];
+      efiInstallAsRemovable = true;
+      efiSupport = true;
+
+      extraEntries = ''
+        menuentry "Reboot" {
+          reboot
+        }
+        menuentry "Poweroff" {
+          halt
+        }
+      '';
+    };
+  };
+}