curl --request GET \
  --url https://core.ravenna.ai/api/custom-fields \
  --header 'x-ravenna-api-token: <api-key>'

{
  "items": [
    {
      "id": "<string>",
      "workspaceId": "<string>",
      "key": "<string>",
      "label": "<string>",
      "description": "<string>",
      "required": true,
      "system": true,
      "config": null,
      "type": "TEXT",
      "options": [
        {
          "id": "<string>",
          "value": "<string>",
          "order": 123,
          "description": "<string>",
          "color": "<string>",
          "icon": "<string>",
          "customFieldId": "<string>",
          "createdAt": "<string>",
          "updatedAt": "<string>"
        }
      ],
      "createdAt": "<string>",
      "updatedAt": "<string>",
      "_count": {
        "requestTypeCustomField": 123
      }
    }
  ],
  "nextCursor": "<string>",
  "totalCount": 123
}