Added webhook healthcheck endpoint

Added the GET /v1/webhooks/health_check endpoint to monitor the status of your webhook system. Poll this endpoint to check webhook delivery health within the last 10 minutes.

Example

The following is an example of a 200 OK response:

{
  "status": "healthy",
  "last_checked": "2025-07-01T00:00:00.000Z"
}

The endpoint returns an "unhealthy" status if webhook deliveries have failed or are experiencing issues within the monitoring window.