feat(sync-engine): introduce pluggable SyncHandler interface in SyncManager (#37)

[rohansaini-02]

Summary

This PR introduces a pluggable SyncHandler interface in SyncManager within the poc-sync-engine package. This decouples queue orchestration from the mock API transport, allowing interchangeable mock or HTTP-backed execution handlers.

Related Issue

Resolves #37

Changes Made

• Handler Abstraction: Defined and exported the SyncHandler interface with a handle(job: SyncJob) signature.
• SyncManager Update: Constructor-injected the SyncHandler dependency and updated drainQueue() to delegate sync processing to it.
• Cleanup: Removed the hardcoded mockFrappeApiCall private helper method.
• Mock Testing: Refactored the test suite to use Jest mocks for asserting handler execution and success states.
• Backoff Validation: Added a new unit test using Jest fake timers (jest.useFakeTimers()) to verify that connection rejections trigger exponential retry backoffs correctly.

Testing Performed

• Ran the unit tests inside poc-sync-engine:

  npm test

  All 5 tests compiled and passed successfully.

[ravencore06]

Hey, did you get any update?

[rohansaini-02]

Hey, did you get any update?

Not yet, most orgs have already notified their selected contributors, but there’s no update on the TAP projects yet