With each approach there is many ways of defining environment variables used in the application and that includes:
Defining a .env file at the root i.e. [NAME]=[VALUE]
Defining in the Dockerfile i.e. `ENV [NAME]=[VALUE]
Defining under [env] in fly.toml
My question is how do you manage for multiple environments i.e. common, development, qa / test, production? The environment variables should be secret and should not be committed to VCS.