Inheritance: System.Net.Http.HttpClient
 public void CreateFailedHttpClientRest()
 {
     HttpClientRest client = new HttpClientRest(
         "xxxxxxxxxxxx",
         "9a4129b37640ea5f62357922975842a1");
 }
 public void CreateHttpClientRest()
 {
     HttpClientRest client = new HttpClientRest(
         "https://api.paymill.de/v2", 
         "9a4129b37640ea5f62357922975842a1");
 }