docs: public SimpleConfiguration orElse(SimpleConfiguration fallback) {
      SimpleConfiguration copy = new SimpleConfiguration(this);
      for (Map.Entry<String, String> entry : fallback.toMap().entrySet()) {
        if (!copy.containsKey(entry.getKey())) {
          copy.setProperty(entry.getKey(), entry.getValue());
        }
      }
      return copy;
    }