Create documents on the company an answer request is about

Uploads documents as the answer to a DOCUMENTS question, filed on the company the request is about. The target company is taken from the request's onBehalfOfCompanyId and is deliberately not accepted in the body, so this grant cannot be aimed at any other company. Only the answering company (forCompanyId) may call it, and only while the brand that issued the request is still connected to it; anyone else gets 404 request_not_found, so the existence of another company's request is never confirmed. Where the generic POST /v3/company-documents/bulk-create requires the target to be in the caller's own network — which a delegated answering party never is — this route treats the request itself as the authorization. Each document is filed on the subject company with the caller as its owner, is never public, and is auto-shared with the brand that asked, which is what makes it visible to all three parties. Files must belong to the caller; any that do not are skipped rather than failing the batch. Responds 201 with the created ids.