OEM partition snapshotting

[anmazzotti]

This is a new feature request for OEM partition snapshotting.

The desire is to be able to create new snapshots when running elemental upgrade.
It also probably makes sense to bind them to system snapshots somehow, so that they can be rolled back together seamlessly.

I am also not sure what the behavior for taking the snapshot should be. Shall the toolkit simply take a snapshot of current OEM, or should the user input a path to take a snapshot from?

[davidcassany]

Yes, ideall would also be nice to check what Micro does for /etc, for which a separate overlayfs layer is kept in persistent area for each snapshot. I wonder if it would make sense adding a flag to snapshot somehow the persistent directories we overlay. Not sure how to handle persistent volumes though 🤔 should we start treating /oem as a special case?