/// <summary>Constructs a new token response exception from the given error nad optional HTTP status code.</summary>
 public TokenResponseException(TokenErrorResponse error, HttpStatusCode?statusCode)
     : base(error.ToString())
 {
     Error      = error;
     StatusCode = statusCode;
 }
 /// <summary>Constructs a new token response exception from the given error.</summary>
 public TokenResponseException(TokenErrorResponse error)
     : this(error, null)
 {
 }