curl --request GET \
  --url https://api.bold-factory.com/v1/items/skus/{skuReference}/properties/optional \
  --header 'Authorization: Bearer <token>'

{
  "results": [
    {
      "id": "<string>",
      "externalReference": "<string>",
      "name": "<string>",
      "createdAt": "2023-11-07T05:31:56Z",
      "createdBy": "<string>",
      "lastModifiedAt": "2023-11-07T05:31:56Z",
      "lastModifiedBy": "<string>"
    }
  ],
  "totalCount": 123
}