6-5 Add User Progress Endpoint

In this lesson, we add an endpoint that fetches the all course progress for a specific user.

By combining our course meta data with all of the LessonProgress objects, we can reconstruct a user’s entire progress — even if there aren’t any LessonProgress objects yet.

We also update the initialize action in our Pinia store to fetch this data on startup, so we always start with the current data.