curl --request GET \
  --url https://api.loyalty.dog/v2/loyalty/programs/{programId}/customFields \
  --header 'Authorization: Bearer <token>'

{
  "detail": [
    {
      "loc": [
        "<string>"
      ],
      "msg": "<string>",
      "type": "<string>",
      "input": "<unknown>",
      "ctx": {}
    }
  ]
}