General
configure .env file - Google Search
https://www.google.com/search?ei=Pd8sXZS2IaTy5gK0oaWYBw&q=configure+.env+file&oq=configure+.env+file&gs_l=psy-ab.3..0i7i30j0l2j0i30j0i8i30.32481.33626..33871...0.0..0.184.786.4j3......0....1..gws-wiz.......0i71j35i304i39j0i8i7i30.dH-q95PgaHkHow to customize Node.js .env files for different environment stages
https://www.freecodecamp.org/news/nodejs-custom-env-files-in-your-apps-fa7b3e67abe1/How to set environment variables for your web apps (for SECRET_KEY etc) | PythonAnywhere help
https://help.pythonanywhere.com/pages/environment-variables-for-web-apps/Configuring Django Settings: Best Practices
https://djangostars.com/blog/configuring-django-settings-best-practices/