curl --request GET \
  --url https://api.titletrackr.com/api/v1/order-fields \
  --header 'Authorization: Bearer <token>'

{
  "core_fields": [
    {
      "key": "<string>",
      "label": "<string>",
      "type": "<string>",
      "required": true,
      "options": [
        "<string>"
      ]
    }
  ],
  "custom_fields": [
    {
      "key": "<string>",
      "label": "<string>",
      "type": "<string>",
      "required": true,
      "options": [
        "<string>"
      ]
    }
  ]
}