Description

f4c39e6 deprecated OS field in the Container struct that is used to persist the on-disk state in favor of a Platform field that contains a full OCI platform information.
A best-effort migration was also added, which attempts to fill the new ImagePlatform field based on the old OS value and the container image.

At some point, we should remove the old field and the migration completely.

However, this will mean that containers created before v28 will be missing the platform information, so that probably needs some time/or a clearer documentation on our support for upgrades.

Also add a warning to the release notes:

TODO: Containers created before v28 need to be recreated.