Add a notification (default: disabled) sent to the teacher when a student completes the course. This requirement has come up previously (see links).

Currently there is an optional notification (default: enabled) sent to the student when they complete the course.

How will we define the teacher? Course participants having capability report/completion:view?

Also, this must respect group mode, i.e. if the course's group mode is "Separate groups" and the teacher does not have capability moodle/site:accessallgroups then the teacher must only receive the notification if they're in the same group as the student.