Consider deprecating old data API

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

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

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

First clarify whether this issue is about deprecating the old data API or adding core import support; the title and body describe different changes. Then locate the configuration handling and the import/data API entry points, and confirm that the intended behavior for `enable_import` defaults to `false` before defining what completion means.

Written by the indexing model from the issue text.