Latest improvements to Webhook API (beta)

We made several improvements to the Webhook API.

• In our App Showcase, we added sample NodeJS and PHP Webhook demo applications. Both highlight all the moving pieces for registering and receiving webhook subscriptions.
• We added a Subscription test payload endpoint that enables you to send a test event payload to your registered webhook URL. This endpoint can help you troubleshoot why your webhook is not receiving events for a subscription. If your webhook is unable to receive the event or returns an error, we indicate the issue in our response. This response indicates the next steps you can take to resolve the issue.
• We added a new Webhook troubleshooting documentation page where we provide information on how to resolve common errors.
• We added a complete, working C# sample application as a companion to the tutorial.
• For many consumers of ModSecurity (a web application firewall often used in Apache and PHP hosting environments to enforce OWASP security suggestions), they rely on a set of core rules. We made a contribution to the OWASP ModSecurity Core Rule Set (CRS) repo in GitHub to add application/cloudevents+json and application/cloudevents-batch+json to their default list of accepted values for the content-type header. Our contribution is tentatively planned as part of their CRS v3.3.0 release. We'll provide an update when this is live!