Since today it's possible to assign a creator when an item is created via API. The creator can be anyone that belongs to the site or the organization. The call must be made using a token with permission to edit the creator.
API users can assign the creator by declaring the type and the ID of the desired creator in the relationship
field of the creation request:
POST https://site-api.datocms.com/items HTTP/1.1X-Api-Version: 3Authorization: Bearer YOUR-API-TOKENAccept: application/jsonContent-Type: application/vnd.api+json{"data": {"type": "item","attributes": { [...] }},"meta": { [...] },"relationships": {"item_type": {"data": {"type": "item_type","id": "44"}},"creator": {"data": {"type": "account","id": "312"}}}}}