added duckdns.nix

systems/jeeves/services/duckdns.nix

@@ -0,0 +1,10 @@
+let
+  vars = import ../vars.nix;
+in
+{
+  services.duckdns = {
+    enable = true;
+    tokenFile = "${vars.storage_secrets}/services/duckdns/token";
+    domainsFile = "${vars.storage_secrets}/services/duckdns/domains";
+  };
+}