curl --request POST \
  --url https://api.arcuserp.com/v1/orders/{id}/items/bulk \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "items": [
    {
      "product_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
      "quantity": 2,
      "variant_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
      "sell_rate": 123,
      "list_price": 123,
      "notes": "<string>"
    }
  ]
}
'

{
  "object": "bulk_add_result",
  "processed": 123,
  "items": [
    {
      "id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
      "order_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
      "product_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
      "variant_id": "3c90c3cc-0d44-4b50-8888-8dd25736052a",
      "sku": "<string>",
      "title": "<string>",
      "quantity": 123,
      "quantity_fulfilled": 123,
      "quantity_returned": 123,
      "sell_rate": 123,
      "list_price": 123,
      "discount_amount": 123,
      "line_subtotal": 123,
      "tax_amount": 123,
      "line_total": 123,
      "unit_cost": 123,
      "weight": 123,
      "is_tax_exempt": true,
      "product_tax_code": "<string>",
      "sort_order": 123,
      "created_at": "2023-11-07T05:31:56Z",
      "updated_at": "2023-11-07T05:31:56Z"
    }
  ],
  "errors": [
    {
      "index": 123,
      "error": "<string>"
    }
  ]
}