Consider deprecating old controllers API

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

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

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

No files, tests, or entry points are named. Start by locating the controllers API, helper filtering, and existing configuration options; done means adding the proposed enable_filtering option with a false default and verifying filtering behavior, while resolving the title's deprecation scope.

Written by the indexing model from the issue text.