docs: public ResponseWrapper addFriends(String username, String... users)
              throws APIConnectionException, APIRequestException {
          StringUtils.checkUsername(username);
          Preconditions.checkArgument(null != users && users.length > 0, "friend list should not be empty");
  
          JsonArray array = new JsonArray();
          for (String user : users) {
              array.add(new JsonPrimitive(user));
          }
  
          return _httpClient.sendPost(_baseUrl + userPath + "/" + username + "/friends", array.toString());
      }