code: public Response addUserToGroups(String username, UserGroupsEntity userGroupsEntity) {
  		return restClient.post("users/" + username + "/groups/", userGroupsEntity,
  				new HashMap<String, String>());
  	}
docs: Adds the user to groups.
  
  @param username
  the username
  @param userGroupsEntity
  the user groups entity
  @return the response