Attachments package

[stevensJourney]

Overview

This adds attachments helper functionality to the PowerSync Core module.

For full context. See the README

This implementation is a combination of the approach taken in the JS and Dart implementations.

• The syncing strategy is adapted from JS. The Dart implementation requires developers to manually diff the watched attachments and local attachments state.
• The JS implementation is a single, large, abstract class. This implementation borrows from the Dart implementation and splits the components into an AttachmentsService which handles Attachment state persisting and a Syncing service which processes the queue.
• The AttachmentQueue here is not abstract, it provides a common and simple default implementation for certain operations. The class is open and can be extended if developers require custom functionality.

Demo

See the small video demonstrating syncing attachments between two devices

attachment_demo.mp4

TODOS

• Complete unit tests
• Use in demos
  • Added to Android Supabase Demo

[Copilot]

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• connectors/supabase/build.gradle.kts: Language not supported
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core/README.md:27

• Consider correcting 'it database API' to 'its database API' for proper grammatical accuracy.

of [SQLDelight](https://sqldelight.github.io/sqldelight/latest/) for it database API and typesafe database