Preview a credit note without creating it

Compute what a credit note would look like against a specific invoice without persisting anything. Use this to validate amounts and show a "here's what will happen" UI before the merchant commits. No side effects — no DB writes, no events emitted, no refunds initiated. Mirrors Stripe's `POST /v1/credit_notes/preview`. --- **Related endpoints** - `GET /credit_notes` — List credit notes - `POST /credit_notes` — Create a credit note - `GET /credit_notes/{id}` — Get credit note by ID - `POST /credit_notes/{id}/void` — Void a credit note - `GET /credit_notes/invoice/{invoice_id}/eligibility` — Check credit note eligibility for an invoice - `GET /credit_notes/transaction/{transaction_id}/reversal-eligibility` — Check reversal eligibility for a transaction - `GET /credit_notes/{id}/lines` — List line items on a credit note **Common errors** - `400 invalid_request` — malformed payload or failed validation. - `401 authentication_error` — missing, invalid, expired, or revoked credential. Codes: `authentication_failed`, `invalid_api_key`, `expired_api_key`, `api_key_revoked`, `session_invalid`, `merchant_required`. Carries a `WWW-Authenticate: Bearer` challenge. - `404 resource_missing` — the referenced resource does not exist or is not visible to your key. **Idempotency** Pass an `Idempotency-Key` header (UUID v4 recommended) to make retries safe. Keys are valid for 24 hours; see [the idempotency guide](/docs/fundamentals/idempotency).

curl -X POST "https://api.revkeen.com/v2/credit_notes/preview" \
  -H "x-api-key: $REVKEEN_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "invoice_id": "660e8400-e29b-41d4-a716-446655440000",
    "amount_minor": 5000,
    "tax_amount_minor": 500,
    "credit_method": "refund_to_payment_method",
    "reason_code": "customer_request"
  }'

{  "data": {    "object": "credit_note_preview",    "invoice_id": "f4c4edb8-11e0-4b33-bcc1-482dc59ebb32",    "proposed_amount_minor": 0,    "proposed_tax_amount_minor": 0,    "currency": "string",    "invoice": {      "id": "497f6eca-6276-4993-bfeb-53cbbbba6f08",      "total_minor": 0,      "amount_paid_minor": 0,      "amount_due_minor": 0,      "previously_credited_minor": 0,      "max_creditable_minor": 0    },    "after_credit": {      "new_amount_due_minor": 0,      "new_amount_credited_minor": 0,      "would_leave_outstanding": true    },    "exceeds_max_creditable": true,    "credit_method": "string"  }}