Add rate limiting for import

**Feature request**
It would be great to have serialization for lib.

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

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

The issue names no files, tests, or entry points. First reconcile the title's import rate limiting with the body’s serialization request and confirm which behavior the `enable_serialization` option should control; done should include the agreed configuration behavior and coverage for its default.

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