Webhook payload for issues is incomplete

I'm trying to write an IRC bot for issues to replace our bugzilla instance (bugzilla.gnome.org).

When trying to write a bot that would notify members of a room of a change (open, close, reopen, added labels), I've noticed the type of notification/event is not actually manifested in the payload.

This means that I need to somehow know in advance what the previews states of the issue were, and calculate the difference to know what actually changed.

It would be rather useful to add some metadata to enable the API consumer to understand what actually changed in the issue.