(RFE) support multiple notification objects based on schedule-end

[sadsfae]

We have a need to expand the notification framework for corner-cases where we have an expansion, which has undergone an extension once but is continued to have that different sub-set of temporary systems expanded further. We have the delta message, denoted by the method create_message in notify.py here:

https://github.com/redhat-performance/quads/blob/master/quads/tools/notify.py#L198

In scenarios such as this, we don't have a good way to handle delta message notifications in harmony with the standard 7,5,3,1 day cloud expiration notices.

This should be considered a general improvement, in that in the current notification codebase we share the same 7,5,3,1 day expiration messages with sets of systems which potentially may have different --schedule-end dates.

What this Covers

• Treat each set of host notification objects as different depending on the system --schedule-end date.
• Send separate 7,5,3,1 day notifications per each notification object set.
• Utilize the delta message logic and notification system to still provide diffs of systems leaving or joining otherwise
• Treat uniform --schedule-end notifications as they were before if there is no deviation in end dates among systems in the same cloud