Update middleware documentation

**Problem**
When working with middleware, 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 middleware error-handling entry points in the repository. Review how current errors are described and determine which details the documentation should cover. Done means the middleware documentation clearly explains the more descriptive error messages and the related error-handling behavior.

Written by the indexing model from the issue text.