Slot shown in calendar_upcoming block of other courses

[t-schroeder]

When you register for a slot in one course a user event is created for you (i.e. an event with userid set, but with courseid, categoryid etc. unset). That event is somehow not visible in the calendar, but it is visible in the calendar_upcoming block, even in other courses. Which makes sense since it's a user event. But it also belongs to a course. Is there a way we can get the event to only show in calendar_upcoming blocks of the course that the organizer activity is in?

[t-schroeder]

This is probably related to #70.