Refactor middleware for better readability

**Problem**
When working with handlers, 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 middleware and handler error-handling entry points in the repository. Review the current error messages and surrounding control flow before deciding the scope. Done means the middleware is easier to read and handler failures produce more descriptive messages, with relevant tests updated or added if they exist.

Written by the indexing model from the issue text.