A typed reference to a running invocation. Returned by sendClient() methods
(wrapped in Future<InvocationReference<O>>), or created via invocation(id).
attach() returns a Future<O> with the serde from the original descriptor.
signal() sends a named signal to the target invocation.
A typed reference to a running invocation. Returned by
sendClient()methods (wrapped inFuture<InvocationReference<O>>), or created viainvocation(id).attach()returns aFuture<O>with the serde from the original descriptor.signal()sends a named signal to the target invocation.cancel()cancels the target invocation.