Dev/Prod Configurations

[raphaeltm]

We need to document the best way to run different configurations in development and production. Even things like environment variables etc. Sometimes you want to add a NODE_ENV=development in dev andNODE_ENV=production in prod. We can tell people to do something like:

defang compose up -f compose.yml -f compose.defang.yml

But that's pretty annoying.

I think it would be nice if the defang CLI looked for a *compose.defang.y*ml file by default, and if it exists, use it to override values in the main compose file.

It's not a full development workflow, but I think it's a decent starting point.