Update validation documentation

**Feature request**
It would be great to have encryption for middleware.

**Use case**
Many users need this functionality for production deployments.

**Implementation idea**
Add a new config option `enable_encryption` with default `false`.

Start by locating the middleware configuration and the code that loads or applies its options. Confirm how `enable_encryption` should affect production deployments, what it encrypts, and how the default `false` behavior is documented. Done means the option is implemented with the stated default and the validation documentation accurately describes its behavior.

Written by the indexing model from the issue text.