feature(openssh): add modules for openssh and openpgp

modules/nixos/gnupg.nix

@@ -0,0 +1,9 @@
+{ config, lib, pkgs, ... }:
+
+{
+  # enable gnupg agent
+  services.gnupg.agent = {
+    enable = true;
+    enableSSHSupport = true;
+  };
+}