Version snapshots have modified_at of when snapshot was created, not when content was last modified
When a collection snapshot is created (recording a version), it appears that modified_at gets set to that point in time. However, because created_at is when version 1 is created, and the same for every snapshot, we don't have a field that tells us when the content of that snapshot came into existence.
In other words, the modifed_at timestamp of a collection snapshot at version N is actually the point in time when version N+1 was created. This is not what we want.
Fix the API server so that snapshots get the modified_at of the collection at the moment the snapshot is taken.
Write a migration that adjust the existing modified_at fields when versioning is enabled. The modified_at of version N should take the modified_at of version N-1. The "modified_at" of version 1 should take the value of "created_at".