code: public AuthRequest renewAuth(String refreshToken) {
          Asserts.assertNotNull(refreshToken, "refresh token");
  
          String url = baseUrl
                  .newBuilder()
                  .addPathSegment(PATH_OAUTH)
                  .addPathSegment(PATH_TOKEN)
                  .build()
                  .toString();
          TokenRequest request = new TokenRequest(client, url);
          request.addParameter(KEY_CLIENT_ID, clientId);
          request.addParameter(KEY_CLIENT_SECRET, clientSecret);
          request.addParameter(KEY_GRANT_TYPE, "refresh_token");
          request.addParameter(KEY_REFRESH_TOKEN, refreshToken);
          return request;
      }
docs: Creates a request to renew the authentication and get fresh new credentials using a valid Refresh Token and the 'refresh_token' grant.
  <pre>
  {@code
  AuthAPI auth = new AuthAPI("me.auth0.com", "B3c6RYhk1v9SbIJcRIOwu62gIUGsnze", "2679NfkaBn62e6w5E8zNEzjr-yWfkaBne");
  try {
  TokenHolder result = auth.renewAuth("ej2E8zNEzjrcSD2edjaE")
  .execute();
  } catch (Auth0Exception e) {
  //Something happened
  }
  }
  </pre>
  
  @param refreshToken the refresh token to use to get fresh new credentials.
  @return a Request to configure and execute.