[FEATURE]: expand terraform support

Feature Request

Background / Motivation

Terraform .13 is out! But also being locked to one version of terraform is pretty limiting 😦

What should the user be able to do?

Specify versions of Terraform besides .12.26.

Why do they want to do this? What problem does it solve?

Use new features / bug fixes in Terraform. for_each for modules!!

Suggested Implementation(s)

Since the CLI interaction with Terraform is pretty stable, I think this would mostly amount to expanding this and doing integration tests. The json output had some changes in .13 but I think it’s just extra fields.

How important is this feature for you/your team?

🌵 Not having this feature makes using Garden painful

[edvald]

It doesn’t exactly wrap/extend the exec module, even though it does execute commands locally. I’d hesitate to require Docker for this, because many users will be unable to use it locally, and we don’t want to preclude use of Terraform before a remote cluster is available.

What I think I’ll do is to simply add the latest 0.13 version, as well as allow a null option for the Terraform version, which will direct Garden to use whichever terraform CLI version that’s on the user’s path.

[jeremiahlewis-vw]

(Will keep pushing for a container-based setup, but understand your justification, thanks!) And thanks for the great tool. 😃