The most common is "How do I set my custom domain" (answer: APP_DOMAIN)
but this also requires setting LUCKY_ENV=production which requires
SECRET_KEY_BASE, DATABASE_URL, and PORT
This patch adds support for development with the Nix package manager. In
order to support the traditional nix-shell tool as well as the (still
experimental) Nix Flakes feature of the upcoming version of Nix, this
patch adds shell.nix *and* flake.nix/flake.lock. Usage instructions
have been added to the README.
