chore: remove unnecesary variable and improve docs

Author: fagiannoni

backend/.env.default

@@ -7,5 +7,5 @@
 ################################################################################################
 
 DATABASE_URL=postgresql://postgres:postgres@db:5432/postgres?schema=public
-REDIS_URI="redis://redis:6379/0"
-PYTHON_ENV=production
+
+PYTHON_ENV=production

backend/app/settings.py

@@ -28,6 +28,7 @@ class Settings(BaseSettings):
     # Why? This way we can control most production values through commits, instead
     # of having to manually set them in the production server. The `.env` in production
     # is reserved only for secrets.
+    # Also, all env variables required to build containers must be set in `.env.default`
 
     # Environment name. Used to select the correct environment variables.
     # Possible values: "development", "production".