Make `TF_IN_AUTOMATION` env var for terraform commands optional

[osterman]

Describe the Feature

Terraform does not check the value of TF_IN_AUTOMATION, only that it is set. As soon as it's set, the behavior takes effect. We hard code this setting, and don't provide a way to unset it.

Expected Behavior

TF_IN_AUTOMATION should be optional.

Use Case

When doing a lot of development with atmos, sometimes it's convenient to also use native terraform commands. If TF_IN_AUTOMATION is set, then it won't emit the terraform command you can run to apply it.

Describe Ideal Solution

Can we simply rely on setting the following in atmos.yml, so that users can change the behavior.

env:
  TF_IN_AUTOMATION: true

Alternatives Considered

No response

Additional Context

No response