When I use removeItem state operator then TypeScript complains that message object can be possibly undefined even though I specified the type for removeItem operator. I could fix the issue with optional chaining but that is not possible if I want to use a utility library like Ramda

![image](https://user-images.githubusercontent.com/14946081/104027016-135aed80-51c7-11eb-9316-9b3dbf5b79bf

Basically, we don't need to have kafka-console-consumer, we have mill instead: https://github.com/ThreeDotsLabs/watermill/tree/master/tools/mill

It would be nice to replace it in all examples.

I would like to review the docs and explain also de concepts behind some decisions.
Things needed to explain:

• DDD objectives and reasons why.
• Core concepts like
  • bounded context
  • anti corruption layer
  • domain
  • value objects VS entities
  • aggregates
  • aggregate root
  • layered architecture and each one responsibility
  • reasons for the command and query bus
  • the even