feat: support terraform_version_file

[v1v]

Closes #298 and #208

What

Add support for terraform_version_file input and keep the backward compatibility to use latest if both inputs are set or only terraform_version.

Why

Take advantage of the existing tools such as https://github.com/asdf-vm/asdf
Use a similar mechanism done in some other setup-<app> actions.

Similar PRs

I was blind, and I didn't see any references to them in the GH issues :/

• utilize .tool-versions file to resolve terraform version #323
• ✨ feat(versionfile): accept versionfile #324

[hashicorp-cla-app]

All committers have signed the CLA.

[danielcompton]

We use .terraform-version which is a quasi-standard for Terraform: https://github.com/tfutils/tfenv?tab=readme-ov-file#terraform-version-file.

[v1v]

Do you mean replace or anything else. for .terraform-version?

I think keeping compatibility with https://github.com/asdf-vm/asdf by using .tool-versions is a good idea, for instance, some other GitHub actions use it:

• https://github.com/updatecli/updatecli-action/#updatecli-version-file
• https://github.com/actions/setup-java/blob/main/docs/advanced-usage.md#Java-version-file

[danielcompton]

The Java action also supports .java-version: https://github.com/actions/setup-java/blob/main/docs/advanced-usage.md.

I think it would be good to mention .terraform-version specifically because a lot of people are probably using it.

[v1v]

Sure, see 149638b (#454)

[briceburg]

Is there a chance we could bake in support for the terraform.required_version block from configuration? Ultimately this decides if terraform will run or not when it's defined and should be considered authoritative?

#407