Lesson: Belong to multiple Courses

[WoodhouseP1]

We currently are migrating our LMS to Sensei, however a number of lessons are repeated across different courses (I.E. how to log in).

The ability to be able to add a Lesson to multiple Courses would mean we have a true single source of truth approach. We could clone the lesson, however, this would mean if the source material changed we would have multiple lessons to change. This means multiple points of failure and risk.

[donnapep]

@WoodhouseP1 I'm closing this as there is already an existing issue for this one.