Hello World :)

These are the parties involved:

payments: The payments core. Is a DDD payments core which allow payment request/reject/approval.
contractor_web_ui: a web UI for contractors. It publishes the payment_requested event to the msg broker, handles the payment_accepted and payment_rejected events coming from the msg broker.
manager_web_ui: a web UI for managers. It publishes the payment_accepted and payment_rejected events to the msg broker, and handles the payment_requested event coming from the msg broker.
relational DB's for each web UI: contractor and manager for storing the local copy of the payment request aggregates.
message broker Kafka for serving as message bus between the 2 web_uis

Process model:

There are 2 processes for each app. Karafka & rails web UI
In addition to those there are the docker managed containers runing the zookeeper & kafka & postgresql processes & redis.

Role of each process:

Kafka serves as a message bus for exchanging events between the consumer and manger app.
Redis serves the Turbo Websocket for Rails 7 for the Realtime UI update.
Postgresql acts as a Relational Database for both Contractor and Manager apps.

docker compose up
cd contractor_web_ui && bundle install && bundle exec rails db:setup && foreman start
open a new terminal app
cd manager_web_ui && bundle install && bundle exec rails db:setup && foreman start

Step.0.1: open http://localhost:3000. Let's call this: Tab1. This incorporates the Contractor Web UI.
Step.0.2: open a new browser tab and open http://localhost:4000. Let's call this: Tab2. This incorporates the Manager Web UI.
Step.1: In Tab1: click request new payment. Then fill the form and request a new payment
Step.2: The payment request added in the Tab1 should appear in Tab2. Now reject/approve as You wish in Tab2
Step.3: Go backIn Tab1. The payment request should have the same state as it was modified in the Tab2 by the manager.

Controller classes:
- manager_web_ui/app/controllers/payment_requests_controller.rb
- contractor_web_ui/app/controllers/payment_requests_controller.rb
Event Handling Code:
- manager_web_ui/app/consumers/payments_consumer.rb
- contractor_web_ui/app/consumers/payments_consumer.rb