Currently, only user badge grants emit webhook events. This change
extends the `user_badge` webhook to emit user badge revocation events.
A new `user_badge_revoked` event has been introduced instead of relying
on the existing `user_badge_removed` event. `user_badge_removed` emitted
just the `badge_id` and `user_id` which aren't helpful for generating a
meaningful webhook payload for revoked(deleted) user badges.
The new event emits the user badge object.
