feat: expose AttachmentQueue's AttachmentContext

[stevensJourney]

Some AttachmentQueue users have a use case for custom saveFile methods. The attachmentService exposes a context to mutate attachment records in a safe manner. Unfortunately, the attachmentService is currently marked as private which means extending classes cannot access it.

The AttachmentsService contains functionality to watch active attachments and obtain an AttachmentContext via a mutex. Users won't likely need to watch the attachment state, but they could need an AttachmentContext - which exposes methods for reading and manipulating AttachmentRecords.

This makes AttachmentContext a public API and adds a small method to AttachmentQueue to access an AttachmentContext.

An example use case for requiring access is available at #983

[changeset-bot]

🦋 Changeset detected

Latest commit: 0bedefe

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 7 packages

Name	Type
@powersync/common	Minor
@powersync/node	Patch
@powersync/op-sqlite	Patch
@powersync/react-native	Patch
@powersync/tanstack-react-query	Patch
@powersync/web	Patch
@powersync/diagnostics-app	Patch

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[simolus3]

We need to run pnpm exec api-extractor run --local to update the API snapshot. Also AttachmentService should be marked as @alpha instead of @internal now since this makes it part of the public API.

[stevensJourney]

We need to run pnpm exec api-extractor run --local to update the API snapshot. Also AttachmentService should be marked as @alpha instead of @internal now since this makes it part of the public API.

It's nice to see the API Extractor in action! After properly examining the current state of the various components. I updated this PR to not expose AttachmentService directly, but rather add a small method to AttachmentQueue to expose a now public AttachmentContext.