Proposal - 'Summary' node for alerts

[AlexGrs]

One great functionality I would love to see in kapacitor would be something like a summary node:

Today we have a StateChangeOnly option where we only receive alerts when the state changes. It would be really nice to receive an email with a summary of the alerts once it's back to normal.

For instance:
10H00 UTC - Warning (--> notification sent)
10H04 UTC - Critical (--> notification sent)
10H10 UTC - OK (--> notification sent)
10h11 UTC - Summary (--> notification sent with details about: incident duration here from 10H00 to 10h10 so 10 minutes)