API campaign donors including uploaded offline gifts

For GiveCampus integrations and API.

The Gifts API returns a project object with id, name and unique_identifier on each contribution; retrieve the supported date/state range and filter the returned project.id to the campaign. The request allowlist has no campaign_id filter. Follow its asynchronous request/status/download workflow and deduplicate gift IDs. Campaign individual offline uploads are a separate dataset, so this Gifts API is not a complete export of offline donors. Use the campaign Offline Gifts export/source upload for that portion and reconcile donors by the approved identity rule. Imported CRM gift-history APIs are another dataset. A replacement external-email integration must account for this gap; confirm any automatic synchronization requirements with the integration owner.