Add TypeScript types for auth

**Problem**
When working with helpers, the error messages could be more descriptive.

**Suggestion**
Improve error handling and add detailed error messages.

**Context**
This would help with debugging and maintenance.

Start by locating the authentication helpers and any existing TypeScript type declarations. Review how those helpers currently report errors and identify the relevant tests or usage sites. Done means the auth helpers have the requested TypeScript types and their error messages provide the additional debugging detail described in the issue.

Written by the indexing model from the issue text.