Add async doc generation to an existing NestJS project

[inigomarquinez]

The AsyncAPI specification is a project used to describe and document message-driven APIs in a machine-readable format. It’s protocol-agnostic, so you can use it for APIs that work over any protocol (e.g., AMQP, MQTT, WebSockets, Kafka, STOMP, HTTP, etc).

It doesn't have a native plugin for NestJS, but there are some OpenSource tools that we may use to generate the documentation of the async communication.