private List<String> prepareEnrollment(String userId, List<Pair<UUID, String>> ids) throws Exception {
List<String> userTicketIds = new ArrayList<String>();
for (int i = 0; i < ids.size(); ++i) {
UUID ticketId = ids.get(i).getFirst();
String eventId = ids.get(i).getSecond();
ParticipationStatus status = ParticipationStatus.ENROLLED;
ModificationStatus modificationStatus = ModificationStatus.CHANGED;
AttendanceStatus attendanceStatus = AttendanceStatus.UNKNOWN;
DateTime enrolledAt = new DateTime(TimeUtil.getCurrentTime() + (ids.size() - i) * 1000);
UserTicket enrollment = new UserTicket(null, userId, ticketId, eventId, "comment", status, modificationStatus, attendanceStatus, null, enrolledAt, enrolledAt, enrolledAt);
userTicketIds.add(storeEnrollment(enrollment));