Production-ready direct-style Scala

Code for the talk from Scalar 2025. The video is available here: https://www.youtube.com/watch?v=Vy-0LL0REnI

How to run locally

1. Start the Kafka broker & associated services using kafka/docker-compose.yml. After some time, the control center should be available at http://localhost:9021.
2. Start the Posgres database & Grafana LGTM stack (monitoring, logging, tracing) using docker-compose.yml. Once again, after some time, the Grafana dashboard should be available at http://localhost:3000. You can login with admin/admin.
3. Start the backend using ./backend-start.sh. This should create the tables and start the API. OpenAPI documentation should be available at http://localhost:8080/api/v1/docs/.
4. The travel page which is shown in the talk uses two external services (which are part of the distributed trace). From an IDE, start the scalar.directdemo.services.PickRandomService and scalar.directdemo.services.TravelModeService apps.
5. You can now try calling the trip service via OpenAPI. Once you do that, you can check in the Grafana dashboard if the trace shows up - after a couple of seconds. Go to "explore" from the "hamburger" menu, then switch from Prometheus to Tempo, switch to "Search" and take a look at the available traces.
6. Finally, copy ui/.env.example as ui/.env and run ./frontend-start.sh. This should open your default browser with http://localhost:8081/. Go to http://localhost:8081/trip and click the button - the backend service should be called.
7. You might also open Kafka's control center, choose the trips topic, then the "Messages" tab, to view the result of the background streaming.