[FEATURE] Webhook solution to get informed about newest header received by pulse

[Damian Orzepowski]

Is your feature request related to a problem? Please describe.
When integrating with pulse I want to be informed that it received a new header.

Describe the solution you'd like
There should be exposed 2 endpoints:

1. to register a webhook by providing URL and eventually some token for authentication solution
2. to unregister a webhook

When a webhook is registered, everytime a new header is stored by Pulse, it should make a request on a registered URL with data of the newest header.