defang provider set

[raphaeltm]

It's annoying to have to pass --provider=aws all the time, and it's unintuitive for a user to have to remember DEFANG_PROVIDER=aws.

It would be nice to have something like defang provider set aws for the current session. It would make it persistent and discoverable for users.

Maybe we could do something like defang provider set aws --make-default as well and just default to your preferred provider.

[lionello]

We could either have some metadata associated with a project (kept locally or in our backend?), or we could (ab)use the compose file:

services:
  service1: …

x-defang-provider: aws

[raphaeltm]

I think a .defang dir would make sense? I think we could make use of that in a few ways.

I think the x-defang-provider also makes sense.

Multiple options doesn't hurt.

[lionello]

@edwardrf added this in #853