Webhooks for policy changes

The service should be able to call external web hook URL (if configured) when policy source code changes.

In order to implement this it would need to provide an endpoint where external clients can subscribe for such web hook events. For example:

POST /{repo}/policy/{group}/{policyname}/{version}/notifychange
{
  "webhook_url":"..."
  "subscriber":"..."
}

Response:

{
  "version":"..."
  "group":"..."
  "name":"..."
}

[IDM.TSA.E1.00008] Webhooks for policy changes

The product MUST allow other components to subscribe for policy changes via webhooks. Clients
MUST be able to give a URL and the product MUST send the relevant payload once there are
policy changes.