Verify webhooks with ngrok’s new Traffic Policy action

The Verify Webhook traffic policy action is a new addition to ngrok's Traffic Policy engine, allowing developers to easily authenticate webhook requests and protect their applications from unauthorized webhooks. This action verifies that webhook requests originate from the intended provider and are intended for the application, protecting against forged requests, man-in-the-middle, and replay attacks. With over 50 supported providers and precise verification logic, the Verify Webhook traffic policy action provides robust protection for webhook integrations. It also supports conditional logic, allowing developers to chain traffic policy rules and use CEL variables to craft custom policies. The action logs events and returns an `action.ngrok.verify_webhook` object containing error codes, messages, and verification results, enabling further analysis and debugging. By applying the Verify Webhook traffic policy action, developers can safely integrate webhooks into their applications without writing verification code, while also leveraging ngrok's flexible and expressive traffic policies to customize their workflows.