Optimize services for large datasets

**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 error-handling code and cataloging the current messages. Define done as having more descriptive errors for the relevant authentication failures, with any existing error-related checks updated to reflect the new wording.

Written by the indexing model from the issue text.