Improve middleware performance

**Feature request**
It would be great to have filtering for models.

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

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

No files or tests are identified. Start by locating the middleware configuration and model-selection paths, then clarify what filtering means, which models are affected, and how the enable_filtering default should behave. Done should include agreed filtering semantics, the configuration option, and tests covering the disabled default and enabled behavior.

Written by the indexing model from the issue text.