public default StreamObserver<SpannerAsyncActionRequest> executeActionAsync(StreamObserver<SpannerAsyncActionResponse> responseObserver)
ExecuteActionAsync is a streaming call that starts executing a new Spanner
action.
For each request, the server will reply with one or more responses, but
only the last response will contain status in the outcome.
Responses can be matched to requests by action_id. It is allowed to have
multiple actions in flight--in that case, actions are be executed in
parallel.
