Add rate limiting for search

**Feature request**
It would be great to have import for config.

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

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

First reconcile the title's search rate-limiting request with the body, which describes importing configuration and an `enable_import` option. No files, tests, or implementation entry points are identified, so locate the relevant configuration-loading and search paths only after the intended change is clarified; done should include an agreed behavior and validation for the default setting.

Written by the indexing model from the issue text.