Update middleware documentation

**Problem**
When working with services, 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 documentation and the existing service error messages. The issue does not name files, tests, or an entry point, so first determine which documentation and error-handling paths are in scope. Done should mean the relevant middleware documentation explains more descriptive error handling and messages.

Written by the indexing model from the issue text.