Fix TF_TOKEN_<host> env var lookup for auth

[shwetamurali]

Description

tfctl documents that it honors Terraform's TF_TOKEN_app_terraform_io env var for auth, but it never actually matched. When building the lookup name, terraformTokenEnvVar uppercased the hostname, so it searched for TF_TOKEN_APP_TERRAFORM_IO instead of the standard lowercase TF_TOKEN_app_terraform_io. Since env var names are case-sensitive, the standard Terraform-style variable was silently ignored.

This aligns the name-building with Terraform CLI's TF_TOKEN_<host> scheme:

• hostname stays lowercase (as normalized)
• hyphens encode as double underscores (__)
• periods encode as single underscores (_)

Testing

• AddedTestTerraformTokenEnvVar

PR Checklist

• Run npx changie new or install changie to prepare a new changelog entry for the next set of release notes.
• Ensure any command changes are sensitive to these global flags:
  • --json — Force machine readable output to stdout. Does not apply to stderr.
  • --markdown — Force markdown output to stdout. Does not apply to stderr.
  • --dry-run — Don't make any actual writes or other mutations. Describe what would have changed to stderr.
  • --quiet — Don't render output to stdout.
• Get the logging interface from the context and add debug logging for interesting conditions and nonfatal situations.
• Run make gen/screenshot if the root command output changes.
• Add the Autocomplete field to positional arguments and flags to assist shell autocomplete.

PCI review checklist

• I have documented a clear reason for, and description of, the change I am making.

• If applicable, I've documented a plan to revert these changes if they require more than reverting the pull request.

• If applicable, I've documented the impact of any changes to security controls.

  Examples of changes to security controls include using new access control methods, adding or removing logging pipelines, etc.

[ctrombley]

Looks good! I think I found an edge case, there are more details in the comment.

[ctrombley]

I noticed that when using a port we can still get mixed-case hostnames. Here's a test case to reproduce:

Suggested change

	},
	},
	{
	name: "mixed-case hostname with port is normalized to lowercase",
	hostname: "App.Terraform.IO:8443",
	expected: "TF_TOKEN_app_terraform_io_8443",
	},

[brandonc]

Can you add a test case from NormalizeHostname that uses unicode characters, as documented in this section of the terraform docs? and make sure it works the same way? It allows dashes to be in the env variable OR as a double underscore.

[ctrombley]

Looks good, thanks @shwetamurali!