Low-level HTTP client with cookie support.
User credentials input helper.
Ensures the current cookie jar represents a valid Blackboard session.
If a quick probe to /ultra/course already returns 200, the method
resolves true immediately.
All credential prompting / caching is delegated to CredentialManager.
true on successful login, false on failure or user cancel.
Handles CAS authentication flow for Blackboard.
Responsibilities
executionparameter on the CAS login page.