code: public BackchannelAuthenticationRequest setParameters(Map<String, String[]> parameters)
      {
          return setParameters(URLCoder.formUrlEncode(parameters));
      }
docs: Set the value of {@code parameters} which are the request parameters
  that the backchannel authentication endpoint of the OpenID provider
  implementation received from the client application.
  
  <p>
  This method converts the given map into a string in
  {@code application/x-www-form-urlencoded} and passes it to
  {@link #setParameters(String)} method.
  </p>
  
  @param parameters
  Request parameters.
  
  @return
  {@code this} object.