Added NixOS module

nix/qddns-module.nix

@@ -42,7 +42,7 @@ in
       script = "${pkg}/bin/qddns-server";
       wantedBy = [ "multi-user.target" ];
       environment.QDDNS_SERVER = cfg.db;
-      ServiceConfig = {
+      serviceConfig = {
         DynamicUser="yes";
         User = cfg.user;
         Group = cfg.group;