Documentation: Running in production - autoscaling

[febus982]

It would be great having documentation on how to run and manage FastStream in a live system. We'll probably want to have a message subscriber application (read container) per topic/channel (in Kafka also per topic partition, can we manage consumer groups?) and understand autoscaling approaches.

[Lancetnik]

I think, it could be useful to add scaling recipe for all brokers to deployment doc

[Lancetnik]

Also, looks like it is related to #743