Add EventStored internal event published to the EventBus when events are
successfully persisted. This allows observability components (metrics,
projections, audit systems) to react to persisted events without coupling
to application code.
Implementation:
- Add EventTypeEventStored constant to define the event type
- Update InMemoryEventStore with optional EventBroadcaster support
- Add NewInMemoryEventStoreWithBroadcaster constructor
- Update JetStreamEventStore with EventBroadcaster support
- Add NewJetStreamEventStoreWithBroadcaster constructor
- Implement publishEventStored() helper method
- Publish EventStored containing EventID, ActorID, Version, Timestamp
- Only publish on successful SaveEvent (not on version conflicts)
- Automatically recorded in metrics through normal Publish flow
Test coverage:
- EventStored published after successful SaveEvent
- No EventStored published on version conflict
- Multiple EventStored events published in order
- SaveEvent works correctly without broadcaster (nil-safe)
Closes#61
Co-Authored-By: Claude Code <noreply@anthropic.com>
