The session to address.
The identity to read the session under. Server-side publishers pass a system/service user — the session row is being addressed by the server, not on a caller's behalf.
Type-specific data; must be JSON-serializable.
OptionalProviderProvider to read the session with. Defaults to the process-global provider (server bootstrap use).
Event type — a key of RealtimeSessionEventPayloadMap.
Input to RealtimeSessionEventService.Publish.