private string ExtractCredential(AuthenticationHeaderValue authorizationHeaderValue)
        {
            if (authorizationHeaderValue.IsNull())
                return string.Empty;

            return authorizationHeaderValue.GetBearerToken();
        }
        private static string[] ExtractCredentials(
            AuthenticationHeaderValue authorizationHeaderValue)
        {
            if (authorizationHeaderValue.IsNull() ||
                authorizationHeaderValue.Scheme != "Basic")
                return new string[] { };

            return authorizationHeaderValue.Parameter                
                .FromBase64()
                .Split(new[] { ":" }, StringSplitOptions.RemoveEmptyEntries);
        }