added support for keys in external files

nix/hm-module.nix

@@ -0,0 +1,15 @@
+{ config, lib, pkgs, ... }:
+let
+  cfg = config.dyn-gandi;
+in {
+
+  options.dyn-gandi = {
+    enable = lib.mkEnableOption null // {
+      description = lib.mdDoc '''';
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+
+};
+}