...
These APIs allows the caller to list all current subscriptions, and register new ones, as well as delete existing subscriptions. When registering a subscription the provided endpoint is validated, and must respond with a HTTP 200 OK when called with a POST request. The request must respond within the default timeout.
Note that webhook events will only be sent out to users that are both registered listeners of the event, and that same user is either a contributor on the affected test, has write access to the affected content or is a User Administrator (depending on the contextObjectType).
The validation request looks something like this:
...