Feature: Dockerized production backend

[M-Foschian]

Since the deployment of the back-end application is a little bit complex, I propose a docker solution which take care of the most.
With docker compose up I put in production the back-end with postgres and the web server (on port 3000).
The docker file take care of create the different secrets needed.

The proccess will be much simpler:

1. clone the repository
2. copy .env.example and customize as needed (leave the {{xxxx}} tokens as they are)
3. the Dockerfile is ready for an onpremise server behind a proxy, but if it's not the case there are few lines to comment in the Dockerfile
4. run the server with proxy_url=https://your.proxy:port docker compose up --build

In my impementation I have an nginx reverse proxy in front of the back-end and the front-end, so the same url is still valid for client and api (with some rewrite tricks)

Hope this is useful for another deployers