// delete user by id
  @RequestMapping(method = RequestMethod.DELETE, value = "/{id}")
  @ResponseBody
  public Map<String, RestStatusDto> deleteUserById(@PathVariable("id") Long id) {
    final Map<String, RestStatusDto> response = new HashMap<String, RestStatusDto>();
    User u = userDao.getByKey(id);
    RestStatusDto statusDto = null;
    statusDto = new RestStatusDto();
    statusDto.setStatus("failed");

    // check if user exists in the datastore
    if (u != null) {
      // delete user group
      userDao.delete(u);
      statusDto.setStatus("ok");
    }
    response.put("meta", statusDto);
    return response;
  }