docs: public final void addString(String key, String... values) {
          if (values == null || Array.getLength(values) == 0) {
              return;
          }
          List<String> list = parameters.get(key);
          if (list == null) {
              list = new ArrayList<>();
          }
          list.addAll(Arrays.asList(values));
          parameters.put(key, list);
      }