Support for multiple external courses transferring in to a single course

[robertbwatson]

From the Use Cases page: https://github.com/SFDO-Sprint-2019-Detroit/transfer-equivalency/wiki/Use-Cases -- we currently support an external course being mapped to multiple internal courses or plan requirements, but we do not support multiple external courses mapping to a single internal course. How might we support this?

Example Scenario: In order for a Mock Community College transfer student to get credit for Mock University's Calculus 101 course, they must have taken both Intro to Calculus and Calculus 101 at Mock Community College.

[robertbwatson]

Perhaps a lookup ("Parent External Course"?) could be added on the External Course that would lookup to a parent External Course record? So, a "Parent External Course" record that would represent the student transferring in a collection of courses from the university -- and a child External Course record for each course with the details about each specific course.

Just throwing the idea out there. I haven't thought about this for more than a few minutes, so it's possible this isn't a good or viable approach...