Message Reader — Compose Rewrite — Scoping and planning

The message view (to be renamed Message Reader) is a large and outdated project. Scoping the changes and the impact it'll have on the app prior to getting started on changes is important. We need to consider not only the new views we wawnt to create, but how we're storing data. A large number of the functions are still using callbacks and not using any form of modern architecture. To transfer the view over to compose, we should do more than just swapping out the XML views for Jetpack Compose components, but also ensuring we're using a stateful MVVM (or MVI-like) structure that allows the view to react to immutable view state changes, rather than using callbacks which would be incredibly inefficient in compose.

This ticket is for planning. Getting an idea of the scope and data flow of the current message view and taking a look at how much we'll have to refactor to move the view from XML layouts and fragments into compose.