public FeatureFlagCacheService(
     IFeatureFlagStorageService storage,
     FeatureFlagOptions options,
     ILogger <FeatureFlagCacheService> logger)
     : this(storage, options, telemetryService : null, logger : logger)
 {
 }
        public FeatureFlagCacheService(
            IFeatureFlagStorageService storage,
            FeatureFlagOptions options,
            IFeatureFlagTelemetryService telemetryService,
            ILogger <FeatureFlagCacheService> logger)
        {
            _storage = storage ?? throw new ArgumentNullException(nameof(storage));
            _options = options ?? throw new ArgumentNullException(nameof(options));
            _logger  = logger ?? throw new ArgumentNullException(nameof(logger));

            _telemetryServiceOrNull = telemetryService;
            _latestFlags            = null;
        }