Calendar events imported from URL into existing calendar does not get updated

How to reproduce

• create a calendar using an external tool, e.g. google calendar
• copy the ics url from the external calendar
• in OpenOLAT create a course
• in the course, enable the calendar tool
• open the calendar, open the config symbol in the calendar toolbar (next to the calendar navigation)
• in the config, select the gears menu at the right side of the calendar 
• choose the import from url link
• past the external ics link
• => OK calendar items are imported
• then, go to the external calendar tool
• modify the calendar entry
• way for 4 hours
• open the OpenOLAT course calendar again
• => NOK: calendar entry is not updated in OpenOLAT

In the logfile a line starting with "Begin to update xx calendars." should appear where xx is a number. The line is missing as the ImportCalendarJob never gets executed. 

The fix is to add the following to the schedulerContext.xml file: 

<ref bean="calendarImportTrigger" /> 

It should also be checked what happens when a course is deleted: it seems the import record is not deleted from the database (o_cal_import_to). It is unclear what happens in such a case. Ideally the import record is deleted on course deletion or on calendar deletion.