Docker-based deploy

The flow

Code is pushed to main on github
CircleCI recieves an event, and start the job:
- It builds a new release docker image from the Dockerfile
- It releases builded image to the registry (docker releases are free). This can be private/public.
VPS server is subscribed to new releases of the package (for example using watchtower).
When new release arrives, VPS:
- downloads the release
- creates a container from it
- shuts down the previous app container (database and other services are not affected)
- starts the new container (downtime is really small)

Commands to manually trigger updates

CI
- Deploy workflow:
  - docker build -t dimamik/lisbon .
  - docker push dimamik/lisbon:latest
Server (needs to have .env file in place)
- ./server$ docker-compose up

Zero down deploys

We could omit downtime by:

When update arrives from circle ci, we're:
- Starting new container with updated release
- Instructing nginx to forward new requests to new container
- Check if there are any open connections to the old server. Stop it when there aren't.