Improve error messages in services

**Problem**
When working with auth, 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-related services and their current error-handling paths. Clarify which failures need distinct descriptive messages and verify that each affected path reports useful debugging context without changing its behavior.

Written by the indexing model from the issue text.