Attribute documents.create to an existing user (API parity with JSON import author-mapping)

When creating documents through the API with an admin token on behalf of workspace members, the created document is always attributed to the token's owner. There's no way to set the author as far as I can tell. I noticed that the JSON importer has this for bulk import and would like to suggest we have the single-document API equivalent of that. I'd like to add an optional createdById to the documents.create request: • Admin-only, and the target user must be in the same team. • fails closed so an unknown or cross-team createdById is rejected rather than silently reassigned - the admin check runs before the user lookup, so the field can't be used to probe whether a user id exists. • documentCreator already parameterises createdById / lastModifiedById, so the route change would be small (the audit event still records the acting admin as the actor, keeping attribution honest and traceable). Does this approach sound reasonable, and would …