public void register(User user, T appointment, User responsibleUser) throws RegisterPeriodOverException, AlreadyRegisteredException, MaximumMemberCountExceededException, NotAllowedException, AppointmentNotFoundException {
List<User> st = getRegisteredUsers(appointment, user);
appointment = getRealAppointment1(appointment);
if (st.contains(user)) {
throw new AlreadyRegisteredException();
}
if (appointment.getRegisterStart().after(new Date()) || appointment.getRegisterEnd().before(new Date())) { //nach dem heutigen Tag -> Anmeldung noch nicht begonnen
throw new RegisterPeriodOverException();
}