FlowHandle(id: StateMachineRunId, progress: Observable<String>, returnValue: ListenableFuture<A>)
FlowHandle is a serialisable handle for the started flow, parameterised by the type of the flow's return value.
id
- The started state machine's ID.
progress
- The stream of progress tracker events.
returnValue
- A ListenableFuture of the flow's return value.