@Override
public void addAppointment(final AppointmentDto appointment) throws IOException {
final Event event = new Event();
final Map<String, String> privateProperties = new HashMap<String, String>();
privateProperties.put(EXT_PROPERTY_EXCHANGE_ID, appointment.getExchangeId());
final ExtendedProperties extProperties = new ExtendedProperties();
extProperties.setPrivate(privateProperties);
event.setExtendedProperties(extProperties);
populateEventFromAppointmentDto(appointment, event);
client.events().insert(calendarId, event).execute();