Allow referring to output from another environment

[tsharks]

Summary

It would be great to make it possible to refer in a .tfvars to outputs from a stack deployed in another environment (in the same project).

Motivation

That would enable sharing a stack between environments. Common use cases are to reuse baseline stacks that deploy possibly expensive resources:

• Sharing a VPC (with NAT Gateways, VPC endpoints, etc)
• Sharing a database

This was asked a while ago on Stackoverflow : https://stackoverflow.com/questions/64874245/how-to-make-the-terraspace-stack-common-for-a-few-environments.