Terragrunt: allow opting into using standard plan artifacts

As per https://docs.spacelift.io/vendors/terragrunt/limitations#mocked-outputs-and-the-apply-phase spacelift specifically DOES NOT use the plan artifacts from the plan phase for TG runs.

The way that the documentation says it it kind of makes sense .. at least as a default ..

I wish there was a way to say "We know better, we'll make sure to avoid using mocked outputs in plans, etc etc" .. and have the regular TF functionality back :)

Like in our TG setup we only use mocks for "validate", but not for other commands ..

dependency "something" {
  config_path = "some path"
  mock_outputs_allowed_terraform_commands = ["validate"]
  mock_outputs = include.global.locals.mocks.some-module
}

So we’d be safe from this particular scenario that is being described.

The alternative seems mildly scary .. you may get entirely different stuff applied than was approved, especially if you manage your state outside of spacelift.