I decided to perform something a bit more simpler than what is suggested
in Django best practices for configuration (having a base configuration
file extended for local, staging and production. I now have a single
configuration file setup for production. I overwrite it using
environment variables that I load with the virtual environment. If the
secret key isn't loaded then we consider that we are in production
environment and must load a .env file located at the root of the
program.
There are 2 mandatory environment variables:

- ALLGO_SECRET_KEY
- ALLGO_DATABASE_PASSWORD

The documentation reference all the environement variables available.

Signed-off-by: Matthieu Berjon <matthieu.berjon@inria.fr>