Nova/VersionedNotificationTransformation

Goal
Transform every legacy notification to the new versioned notification framework.

How to do it

 * Check the notification devref that describes the new framework: http://docs.openstack.org/developer/nova/notifications.html
 * Check the existing transformation patches that are merged: http://burndown.peermore.com/nova-notification/
 * Select a transformation from the table on http://burndown.peermore.com/nova-notification/ You can take a patch with status TODO or you can check if a patch that is INPROGRESS needs help.
 * Propose a transformation patch based on the examples.
 * Make sure that you create a new sample file under doc/notificaiton_samples/
 * Make sure that you add a notification sample test under nova/tests/functional/notification_sample_test/
 * If you got stuck you can ask questions from gibi on IRC or join the weekly notification subteam meeting https://wiki.openstack.org/wiki/Meetings/NovaNotification

Tasks
Please use the https://review.openstack.org/#/q/topic:bp/versioned-notification-transformation-rocky topic for the transformation commits

[http://burndown.peermore.com/nova-notification/ The burndown chart is updated hourly from gerrit. ] You can see what to transform and what to review there.

There are three types of transformations:
 * category: instance-payload: The easy ones that uses the same payload as instance.delete
 * category: extended-instance-payload: The complex instance. notifications that needs payload extension.
 * category: specific-payload: The rest that needs specific payload

If something doesn't show up on the burndown then please ping gibi on IRC.