Improve error messages in core

**Description**
Currently auth lacks proper serialization support.

**Proposed solution**
Add configurable serialization with sensible defaults.

**Priority**: Low/Medium

Start by locating the core authentication path and any existing error-message or serialization handling. Clarify the supported serialization formats, configuration surface, and default behavior with maintainers; done means authenticated data serializes consistently under configured and default settings.

Written by the indexing model from the issue text.