Finalize attachment

Finalize a previously uploaded listing attachment and persist it on the listing.

This is step 2 of the listing attachment workflow and must be called after a successful direct upload.

Validation and integrity checks:

• Listing must belong to the authenticated seller and remain active.
• id must match the expected listing-scoped attachment URN format.
• Uploaded image must no longer be in draft state.

Moderation:

• The uploaded image is downloaded and passed through moderation checks.
• Rejected images are deleted and the API returns 451 with rejection reasons.

Side effects:

• Persists a listing attachment record when validation succeeds.
• Re-evaluates listing validity:
  • If the listing requires a photo (price >= 2000 or grading metadata present), finalizing an attachment marks the listing as valid: true.

Response:

• Returns the persisted attachment identifier and public URL.