Comment 5 for bug 1704135

Am I correct in assuming that the upgrade itself will be made by charms itself?

Would it make sense to add 'updgrade-series' hook, that will take care of series upgrades?

I'm asking because I can envision multiple scenarios (mainly with databases) where series upgrade can't be just done with 'do-release-upgrade' but will require coordination from the deployed units (thinking about various databases that will need to be upgraded one-by-one, esp if they are in HA setup).