Transaction Reconciliation

You are given two lists:

1. A list of events, each with a unique event_id and an amount.
2. A list of settlements, each with a settlement_id and a list of event_ids that the settlement is supposed to cover.

Your task is to reconcile each settlement against the events it references. For every settlement compute the sum of the amounts of its referenced events. Then classify the settlement into one of three categories:

• matched: the settlement amount equals the summed amount of its events.
• partial: the settlement amount is less than the summed amount.
• over_matched: the settlement amount is greater than the summed amount.

If a settlement references an event_id that does not exist, treat the amount of that event as 0. After processing all settlements, also report which events were never referenced by any settlement (unmatched events).