using RestSharp;


var options = new RestClientOptions("https://api.sandbox.{id}.gr4vy.app/digital-wallets/click-to-pay/session");
var client = new RestClient(options);
var request = new RestRequest("");
request.AddHeader("Authorization", "Bearer <token>");
request.AddJsonBody("{\n  \"checkout_session_id\": \"fe26475d-ec3e-4884-9553-f7356683f7f9\"\n}", false);
var response = await client.PostAsync(request);

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

{
  "digital_payment_application_id": "DPA ID",
  "digital_payment_application_name": "DPA name"
}