https://hexdocs.pm/phoenix/deployment.html
https://felt.com/blog/elixir-configuration
https://hexdocs.pm/elixir/1.13/library-guidelines.html#avoid-application-configuration
https://elixirforum.com/t/creating-env-file-for-secret-keys/51037
https://devato.com/post/handling-environment-variables-in-phoenix
https://www.theerlangelist.com/article/rethinking_app_env