Can we get rid of EventKind::LockConfirmedAfterFinality?

[luckysori]

This is the event:

https://github.com/itchysats/itchysats/blob/fcb95fbcd9c5d4e8b26e64073b765f24a804ca1a/model/src/cfd.rs#L360-L366

My arguments would be:

• The name implies that it's not just an event. It's actually an event depending on the state. Is that an indication that it shouldn't be an event? I tend to think so. This might apply to other events in this enum i.e. the ones with Prior or Post in their name.
• There is only one place where we handle this event differently than the sibling LockConfirmed. It's in position_metrics::Cfd::apply, and the same could be achieved by inspecting the current state.

Current version:

match event.event {
    // ...
    LockConfirmed => Self {
        state: AggregatedState::Open,
        ..self
    },
    // ...
    LockConfirmedAfterFinality => Self {
        // This event is only appended if lock confirmation happens after we spent from lock
        // on chain. This is for special case where collaborative settlement is triggered
        // before lock is confirmed. In such a case the CFD is closed
        state: AggregatedState::Closed,
        ..self
    },
    // ...
}

Example proposal:

match event.event {
    // ...
    LockConfirmed => match self.state {
        AggregatedState::New
            | AggregatedState::Open
            | AggregatedState::Failed
            | AggregatedState::Rejected => Self {
                state: AggregatedState::Open,
                ..self
            },
        AggregatedState::Closed | AggregatedState::Refunded => self,
    },
    // ...
}

---

This popped into my head whilst thinking about #2465. I imagine that a good solution to that problem will depend on changing our events (or at least using them differently), so it might be a good idea to rethink some of the states before we add new ones.