* @param discloser the mail posting discloser
     */
    protected void sendToSlack(final CardView cardView, final SMailPostingDiscloser discloser) {
        // https://api.slack.com/messaging/webhooks#posting_with_webhooks
        final FessConfig fessConfig = ComponentUtil.getFessConfig();
        final String slackWebhookUrls = fessConfig.getSlackWebhookUrls();
        if (StringUtil.isBlank(slackWebhookUrls)) {

- **Admission webhooks:** Admission webhooks are in widespread use as a Kubernetes extensibility mechanism and have been available in beta since the 1.9 release. The 1.16 release marks the graduation of admission webhooks to general availability (GA).

- Fixed an issue where the API server did not send impersonated UID to authentication webhooks. ([#116681](https://github.com/kubernetes/kubernetes/pull/116681), [@stlaz](https://github.com/stlaz)) [SIG API Machinery and Auth]

- Kube-apiserver: Authorization webhooks now report the following metrics:
  - apiserver_authorization_webhook_evaluations_total
  - apiserver_authorization_webhook_duration_seconds

- Kube-apiserver: timeouts configured for authorization webhooks in the --authorization-config file are now honored, and webhook timeouts are accurately reflected in webhook metrics with result=timeout ([#125552](https://github.com/kubernetes/kubernetes/pull/125552), [@liggitt](https://github.com/liggitt)) [SIG API Machinery, Auth and Testing]

        super.setUp();
        notificationHelper = new NotificationHelper();
    }

    public void test_sendToSlack_withBlankWebhookUrls() {
        // Setup mock configuration with blank webhook URLs
        ComponentUtil.setFessConfig(new MockFessConfig() {
            @Override
            public String getSlackWebhookUrls() {
                return "";
            }
        });

    /** Property key for Slack webhook URLs configuration. */
    public static final String SLACK_WEBHOOK_URLS_PROPERTY = "slack.webhook.urls";

    /** Property key for Google Chat webhook URLs configuration. */
    public static final String GOOGLE_CHAT_WEBHOOK_URLS_PROPERTY = "google.chat.webhook.urls";

    /** Property key for browser locale usage in search configuration. */

- Changed apiserver to treat failures decoding a mutating webhook patch as failures to call the webhook so they trigger the webhook failurePolicy and count against metrics like `webhook_fail_open_count` ([#131627](https://github.com/kubernetes/kubernetes/pull/131627), [@dims](https://github.com/dims)) [SIG API Machinery]

- Added support for CEL expressions to `v1alpha1 AuthorizationConfiguration` webhook `matchConditions`. ([#121223](https://github.com/kubernetes/kubernetes/pull/121223), [@ritazh](https://github.com/ritazh))

- kube-apiserver: Promoted `AuthorizeWithSelectors` feature to beta, which includes field and label selector information from requests in webhook authorization calls. Promoted `AuthorizeNodeWithSelectors` feature to beta, which changes node authorizer behavior to limit requests from node API clients, so that each Node can only get / list / watch its own Node API object, and can also only get...