[Improvement]: Persistence Changes Experiment

[azooz2003-bit]

Description

I realized from looking at the open-source Canvas iOS repo, that there's a simpler way of implementing decoding, saving, etc. into one function:

1. For each model, we create a DTO struct. So for Quiz we have QuizDTO. This will be used to seamlessly decode from an API response. We'll also have a DTO associated type.
2. We'll have a flush (or save) method in each model which takes in the corresponding DTO. It will find the associated @Model entry and return it. It effectively handles merging and inserting into a specific model context. The model context will probably be per user, flush shouldn't decide.
3. Because of the above, I'll remove the Codable conformance from Cacheable. We'll also remove the merge functions since above handles it.
4. We'll experiment with @Relationship types, but parentId approach still works really well. I'm unsure about making parentId an array, I'll think about use cases for that before deciding. Otherwise it's redundant.

Relevant Resources

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• Design Mockups: Figma File
• API Docs: Apple Swift Documentation

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Implementation Plan (optional)

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