/// <summary>
        /// Signs out user and deletes push notification registration.
        /// </summary>
        public async Task SignOutAsync()
        {
            await _authenticationHandler.LogoutAsync();

            // Delete push notification registration for the user.
            var registrationClient = new NotificationRegistrationClient();
            await registrationClient.DeleteRegistrationAsync();
        }
        /// <summary>
        /// Signs out user and deletes push notification registration.
        /// </summary>
        public async Task SignOutAsync()
        {
            await _authenticationHandler.LogoutAsync();

            // Delete push notification registration for the user.
            var registrationClient = new NotificationRegistrationClient();
            var statusCode         = await registrationClient.DeleteRegistrationAsync();

            if (statusCode != HttpStatusCode.OK)
            {
                _telemetryClient.TrackTrace("Push notification deletion failed.");
            }
        }