saveAll

Saves snapshots, each exactly as save would (the version guard, a stale mark for a higher state revision), and returns their outcomes in the same order: the snapshot subscription writes what it coalesced from a batch of entries with one call, so a backend may write them together to share the round trips. A batch that holds a ref more than once is applied as saving its snapshots in that order (SnapshotSaveOutcome.rounds). A snapshot the backend fails to save alone is SnapshotSaveOutcome.Failed; a failure of the whole call, the database unreachable say, is thrown. By default they are saved one by one.