{  
   "data_asset":{  
      "ref":"a3751f0b-24f2-4d7a-be55-ec7f3d3547f3",
      "project_ref":"0a0a20e8-e8a8-4710-b90a-6df3ff775b04",
      "properties":{  
         "attachment_ref":"a8ecacef-2b40-472c-995b-78269b26e1bb"
      },
      "app_data":{  
         "some_custom_field":"a value"
      }
   }
}