Should we future-proof our state files with serde(flatten)?
Right now, our state files parsing will drop unknown fields. That might not be the best option; instead, we might want to preserve and re-serialize unknown fields so that we can preserve any state that's added by a future version of Arti.
The serde(flatten) mechanism might be appropriate for that. But before we apply it, we should probably think about whether this is actually what we want to do, and we should gain a little more experience with this state file mechanism.