We're sending an attendance notification to students 5 minutes before the start time of teaching activities.

Students have asked for a second reminder notification 5 minutes before the scheduled end of the teaching activity if they haven't already checked-in.

We can't do this at present because notifications can only be set from the start time, and our teaching activities are different lengths. Also we don't want to interrupt the activity by sending a notification part way through.

So we'd like to send notifications based on the end time of the activity as well as the start time.