using RestSharp;


var options = new RestClientOptions("https://api.sandbox.{id}.gr4vy.app/gift-card-service-definitions/{gift_card_service_definition_id}");
var client = new RestClient(options);
var request = new RestRequest("");
request.AddHeader("Authorization", "Bearer <token>");
var response = await client.GetAsync(request);

Console.WriteLine("{0}", response.Content);

{
  "id": "qwikcilver-gift-card",
  "type": "gift-card-service-definition",
  "display_name": "Stripe",
  "fields": [
    {
      "key": "private_api_key",
      "display_name": "Private API key",
      "required": true,
      "format": "text",
      "secret": true
    }
  ],
  "icon_url": "https://cdn.gr4vy.app/stripe.svg"
}