refactor(mobile): split store into entity and model

[shenlong-tanwen]

Changes made

• Refactored the App Store to use the repository pattern
• Split the Entity into two - Entity and Model / DTO to make it easier to replace the entity alone in the future
• Moved the store repository to the domain folder. The idea is to have all business logic and handling inside the domain layer and expose the services to the presentation layer

lib/
├─ domain/
├─ presentation/
├─ utils/

• The old store values are migrated to the new entity during the migration.
• A stub User entity and DTO to add and remove them to the new store. The old User entity and repository has to be migrated to use the new ones during the user entity split

TODO

• Domain test cases for the store

[alextran1502]

what is the accessor and should we spell out the whole word as user?

[alextran1502]

Do we need nestTxn? I haven't seen this mechanism used in the backend or current mobile codebase?

[alextran1502]

the Store.I.xxx is singleton I assume? What is the notion of I borrow from? is it from .NET world? :D

[alextran1502]

The PR is not completed yet, correct? I tried to run it on the phone and still running into many errors

lib/pages/share_intent/share_intent.page.dart:22:37: Error: Undefined name 'StoreKey'.
        db_store.Store.get(db_store.StoreKey.serverEndpoint);
                                    ^^^^^^^^
lib/pages/share_intent/share_intent.page.dart:22:18: Error: Undefined name 'Store'.
        db_store.Store.get(db_store.StoreKey.serverEndpoint);
                 ^^^^^
lib/repositories/album.repository.dart:50:38: Error: Member not found: 'Store.get'.
        (q) => q.isarIdEqualTo(Store.get(StoreKey.currentUser).isarId),
                                     ^^^
lib/repositories/album.repository.dart:54:44: Error: Member not found: 'Store.get'.
        (q) => q.not().isarIdEqualTo(Store.get(StoreKey.currentUser).isarId),