Improve error messages in data

**Feature request**
It would be great to have search for handlers.

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

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

No files, tests, or entry points are named. Start by locating configuration parsing and handler discovery, then determine how production deployments should search handlers and where enable_search belongs; done means the option defaults to false and the requested search behavior is covered by tests.

Written by the indexing model from the issue text.