code: function deleteCalendarObject(calendarObject, options) {
    return webdav.deleteObject(calendarObject.url, calendarObject.etag, options);
  }
docs: @param {dav.CalendarObject} calendarObject target calendar object.
  @return {Promise} promise will resolve when the calendar has been deleted.
  
  Options:
  
  (dav.Sandbox) sandbox - optional request sandbox.
  (dav.Transport) xhr - request sender.