b3b3ef98b2
The GA transformer adds the context.course_id property of a tracking log event to the event transmitted automatically to Segment in the "label" property, so GA can use it. This adds it also to the "courserun_key" property, so that regular users of Segment events can also query it in a more consistently-named property. However, it does so only if it is a valid CourseKey. For DENG-997. Add CourseKey parsing.