Correlation ID
Identifies a cross-domain business process. Not a domain entity ID (like order_id or game_id) - it's the identifier for the workflow/transaction that spans domains. Stable across all events in that process.
Propagation rules:
- Client must provide correlation_id on the initial command if cross-domain tracking is needed
- Framework does NOT auto-generate correlation_id - if not provided, it stays empty
- Once set, angzarr propagates correlation_id through sagas, PMs, and resulting commands
- Process managers require correlation_id - events without one are skipped