Repeating completions currently crates a savepoint when a completion
popup was triggered (so after the request completed). Just like for
normal completions the savepoint must be created at the request.
The occurrence of the completion request was previously not saved in
`last_insert`. To that end a new `InsertEvent::RequestCompletion`
variant has been added. When replayed this event creates a snapshot
that is "actived" by the `TriggerCompletion` event and subsequently
used during any `InsertEvent::CompletiuonApply` events.