public CASAuthenticationService(ShellSettings settings, 
            IClock clock, 
            IContentManager contentManager, 
            IHttpContextAccessor httpContextAccessor,
            ICasIdentityRetriever casIdentityRetriever) {
            _settings = settings;
            _clock = clock;
            _contentManager = contentManager;
            _httpContextAccessor = httpContextAccessor;
            _casIdentityRetriever = casIdentityRetriever;

            Logger = NullLogger.Instance;

            ExpirationTimeSpan = TimeSpan.FromDays(30);
        }
        public CASAuthenticationService(ShellSettings settings,
                                        IClock clock,
                                        IContentManager contentManager,
                                        IHttpContextAccessor httpContextAccessor,
                                        ICasIdentityRetriever casIdentityRetriever)
        {
            _settings             = settings;
            _clock                = clock;
            _contentManager       = contentManager;
            _httpContextAccessor  = httpContextAccessor;
            _casIdentityRetriever = casIdentityRetriever;

            Logger = NullLogger.Instance;

            ExpirationTimeSpan = TimeSpan.FromDays(30);
        }