Please extent the api to let the pipeline accept input and return output

[thomaseyde]

I have this scenario where I need to move data for many customers. I have a pipeline as follows, which does the job:

await patterns
              .WithContext(context)
              .RunActivity<ReadCustomers>()
              .FanOutFanIn<ExtractUploads>(new FanOutFanInOptions(1, 50))
              .FanOutFanIn<PrepareUploadBatches>(new FanOutFanInOptions(1, 50))
              .FanOutFanIn<MoveUploadBatches>(new FanOutFanInOptions(1, 50))
              .ExecuteAsync();

Sometimes, however, it is interesting to move data for a single customer. But I cannot do that easily, since there is no way to send input into the pipeline.

If it also were possible to capture output, the pipeline could be used in sub-orchestrations, which would open many options.