When changing snapshot retention, prompt user to apply new policy to existing snapshots
Currently when you change the snapshot schedule, the changes only apply to NEW snapshots.
Please allow the user the option to apply the new policy automatically to all existing snapshots. Or at the very least, notify them of them of snapshots that exist which do not meet the current policy!
Let me provide an example of the problem. If you have a retention policy of 10 days and on DAY1 you change it to 30 days, your retention will look like this:
DAY1 - 10 snapshots
DAY2 - 10 snapshots
DAY10 - 10 snapshots
DAY11 - 11 snapshots
DAY12 - 12 snapshots
DAY30 - 30 snapshots
It takes 30 days to build up to the desired number of retained snapshots, even though you already had 10 perfectly good snapshots you could have kept if their expiration was bumped to creationTime+30d.
This problem exists in other direction, too. Let's say you reduce your retention from 30d to 10d, it will look like this:
DAY1 - 30 snapshots
DAY2 - 29 snapshots
DAY15 - 25 snapshots (15 of them are 15+ days old!)
DAY16 - 24 snapshots
DAY20 - 20 snapshots (10 are 20+ days old!)
DAY30 - 10 snapshots
At DAY20 you have snapshots from 1-10 days and 20-30 days ago, with a wonky gap between 20-30 days.