intervalStart
abstract suspend fun intervalStart(wideEventId: Long, key: String, timeout: Duration? = null): Result<Unit>
Start a named interval inside the flow.
If timeout elapses before intervalEnd, flowFinish or flowAbort, the flow auto-finishes with FlowStatus.Unknown and is sent. Explicit finish/abort cancels any pending timeouts.
Parameters
wideEventId
ID of the wide event.
key
Interval key (e.g., "token_refresh_duration").
timeout
Optional duration for auto-finish.