Write a guide for setting up a pipeline (postgres -> kafka)

[lovromazgon]

This one is a bit more advanced than #1854, it already requires some setup (running Postgres and Kafka), creating some tables and data in the source and then consuming the data from Kafka to prove it reached the destination.

If possible, try to find a docker container for Postgres that already has some data included, or possibly has a table that is continuously getting data inserted/updated by an agent, or something.

[raulb]

We can probably rely on @hariso 's https://github.com/hariso/docker-containers/tree/main/postgresql and add some inserts, etc.