Return lesson events for partitipant

Is so far missing.

changed milestone to /AlekSIS%"[NLnet #3 (closed)] Implement new course book"

assigned to @permcu

created branch 244-return-lesson-events-for-partitipant to address this issue

mentioned in merge request !349 (merged)

closed with merge request !349 (merged)

mentioned in commit 093f23f4