curl --request GET \
  --url https://prod-api.raisedonors.com/api/CustomField/List \
  --header 'Authorization: <api-key>'

{
  "items": [
    {
      "id": 123,
      "name": "<string>",
      "entityType": "<string>",
      "dataType": "<string>",
      "source": "<string>",
      "isEnabled": true,
      "rank": 123,
      "required": true
    }
  ],
  "total": 123
}