code: public User addUser(User user, boolean sendEmail) throws SmartsheetException {
          return this.createResource("users?sendEmail=" + sendEmail, User.class, user);
      }
docs: Add a user to the organization, without sending email.
  
  It mirrors to the following Smartsheet REST API method: POST /users
  
  Exceptions:
  - IllegalArgumentException : if any argument is null
  - InvalidRequestException : if there is any problem with the REST API request
  - AuthorizationException : if there is any problem with the REST API authorization(access token)
  - ResourceNotFoundException : if the resource can not be found
  - ServiceUnavailableException : if the REST API service is not available (possibly due to rate limiting)
  - SmartsheetRestException : if there is any other REST API related error occurred during the operation
  - SmartsheetException : if there is any other error occurred during the operation
  
  @param user the created user
  @param sendEmail whether to send email
  @return the user object limited to the following attributes: * admin * email * licensedSheetCreator
  @throws SmartsheetException the smartsheet exception