refactor: mkHost load-all infrastructure and convert simple features

features/gnupg.nix

@@ -1,9 +1,36 @@
 {
-  nixos = _: {
-    programs.gnupg.agent = {
-      enable = true;
-      enableSSHSupport = true;
-      enableExtraSocket = true;
+  nixos =
+    { config, lib, pkgs, ... }:
+    let
+      cfg = config.features.gnupg;
+    in
+    {
+      options.features.gnupg = {
+        enable = lib.mkEnableOption "gnupg";
+
+        yubikey.enable = lib.mkOption {
+          type = lib.types.bool;
+          default = false;
+        };
+      };
+
+      config = lib.mkIf cfg.enable (lib.mkMerge [
+        {
+          programs.gnupg.agent = {
+            enable = true;
+            enableSSHSupport = true;
+            enableExtraSocket = true;
+          };
+        }
+
+        (lib.mkIf cfg.yubikey.enable {
+          environment.systemPackages = with pkgs; [
+            yubikey-personalization
+            yubikey-manager
+          ];
+
+          services.pcscd.enable = true;
+        })
+      ]);
     };
-  };
 }