Discussion Items do not include workflow in the export

If Discussion Items are set to use `comment_review_workflow`, the workflow information is not included as part of the export, so all are imported as `pending`

Start by tracing the export path for Discussion Items configured with `comment_review_workflow`. Verify how workflow information is serialized and how the corresponding import handles it; done means exported items retain their workflow state instead of all being imported as `pending`.

Written by the indexing model from the issue text.