While it is possible to configure Webhook notifications in the plan, additional headers that might be required for the webhook consumer can't be added at the plan level. 

Currently, admin privileges are required to modify the webhook template, which allows you to set/modify the request headers.

Providing an option to configure headers when webhook notification is selected would be beneficial, as the endpoints might require additional headers for the request.

Along with the option in the UI, the specs parameter should also be added for header configuration for webhook notifications.