Register one or both of the owner's ID document slots (`id_document_front`, `id_document_back`). Each `file_id` must come from a fresh `POST /api/external/customer/{customer}/owner/{owner}/file/presigned-url` call. Send only the slots you want to set or replace. **Lock guards.** - The parent customer must be in `PENDING` or `REJECTED`. Calls against a `PROCESSING` or `VERIFIED` customer return `400`. - The owner itself must be in `PENDING` or `REJECTED`. Calls against an `APPROVED` or `PROCESSING` owner return `400`. - Replacing a file on a previously `REJECTED` owner automatically resets that owner's `status` to `PENDING` and clears its `admin_comments` — the corrected record is re-routed through review on the next `/submit`. **File checks.** The server verifies S3 existence, file size (max 25 MB), and MIME type (PDF, JPEG, or PNG) before persisting. **Slot vs. type consistency** is enforced at `/submit` time, not on this call. The eventual rule is: - `passport` → `id_document_front` only; `id_document_back` must be absent. - `drivers_license`, `id_card`, `resident_permit` → both `id_document_front` and `id_document_back` are required. If you change the owner's `id_document_type` later, make sure the slot set still matches — otherwise `/submit` will reject the customer. All uploaded documents must be **clear, legible, and authentic**. Blurry, cropped, obscured, or otherwise unclear images will be rejected. Fraudulent or falsified documents will not be tolerated — repeated attempts to submit false or invalid documents will result in the customer being **permanently blacklisted** from the platform. There are no exceptions or compromises. Required scope: `customer:write`.