Workload Identity Federation TF Bootstrapping Scripts only support Environment based subjects at the moment

[raykao]

Currently by design (for testing) the input variables for the bootstrapping scripts only support the GH Actions Environment entity as the subject/context for the identity.

This is to quickly test out functionality for now and will add ability to specify Entity Type [Environment, Pull Request, Tag, Branch] as well as the corresponding entity name (e.g. Branch Name, Tag Name, Environment name; PR does not need an entity name)