curl --request POST \
  --url 'https://app.smartsend.io/api/v1/website/{team}/shipments/labels/combine?api_token=' \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "shipments": [
    {
      "shipment_id": "c5540f2b-3eea-45c4-957a-9d7b53f899e7"
    }
  ]
}
'

{
  "data": {
    "type": "combined_label",
    "shipments": [
      {
        "shipment_id": "c5540f2b-3eea-45c4-957a-9d7b53f899e7",
        "shipment_internal_id": "870006543",
        "shipment_internal_reference": "123",
        "carrier_code": "postnord",
        "carrier_name": "PostNord",
        "parcels": [
          {
            "parcel_id": "c5540f2b-3eea-45c4-957a-9d7b53f899e7",
            "parcel_internal_id": "88654389",
            "parcel_internal_reference": "223",
            "carrier_code": "postnord",
            "carrier_name": "PostNord",
            "tracking_code": "DK123456789",
            "tracking_link": "https://smartsend.io/tracking/DK123456789"
          }
        ]
      }
    ],
    "pdf": {
      "link": "https://example.com/labels/DK123456789.pdf",
      "base_64_encoded": "<base64-encoded-pdf-here>"
    }
  }
}