Add rate limiting for export

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

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

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

The title requests export rate limiting, while the body requests backup for handlers and an `enable_backup` configuration option. Start by locating the export and handler entry points and the configuration definition; clarify which behavior is intended before coding. Done should include an agreed scope and acceptance criteria, which the issue currently does not provide.

Written by the indexing model from the issue text.