Add rate limiting for search

**Feature request**
It would be great to have export for parsers.

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

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

First clarify the conflict between the title, which requests search rate limiting, and the body, which requests parser export. Then locate the parser configuration entry point and determine how `enable_export` should be exposed with a default of `false`; done requires the intended production use case and behavior to be specified and tested.

Written by the indexing model from the issue text.