{
  "endpoint": "issueInvoice",
  "description": "Eine Reservierung gehoert zu einem Artikel: ohne articleId keine reservationId",
  "request": {
    "idempotencyKey": "ex-20",
    "priceMode": "gross",
    "serviceStart": "2026-10-06",
    "items": [
      {
        "description": "Kaisersemmel",
        "quantity": 6,
        "unitPriceCents": 65,
        "vatRate": 10,
        "reservationId": "res_example"
      }
    ]
  },
  "expected": {
    "ok": false,
    "code": "validation",
    "fields": [
      "items[0].articleId"
    ]
  }
}