async function start() {
    logger.info('Starting CalDAV service');
    interval = setInterval(syncAllUsers, 1000 * 60 * 30);
    webcalInterval = setInterval(syncAllUsersWebcals, 1000 * 60 * 60 * 12);
  }
@public
@description This function starts the CalDAV service
and start interval to sync all users CalDAV calendars every 30mn
and start interval to sync all users Webcals calendars every 12h.
@example
gladys.services.caldav.start();