Add unit tests for middleware

**Feature request**
It would be great to have serialization for controllers.

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

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

Start by locating the middleware, controller, configuration, and existing unit-test patterns in the repository. Confirm how controller serialization should behave, then cover the new enable_serialization option with its default set to false and verify the serialization behavior in tests.

Written by the indexing model from the issue text.