Refund Allocation Engine

Build a payment management system that processes transactions with priority ordering (credit > credit_card > PayPal) and generates refunds intelligently. For each payment type, the system should only refund the most recent transaction (latest timestamp) until the target refund amount is satisfied. For example, if you have payment1: credit $100 at t=5 and payment2: credit $50 at t=10, and need to refund $120, the system should first refund from payment2 ($50), then from payment1 ($70). You are given a list of payments, each with a unique paymentId, a method enum {CREDIT, CREDIT_CARD, PAYPAL}, an amount, and an ISO-8601 timestamp string. Implement a function that returns the list of refunds (paymentId and amount) that satisfy the target refund amount while respecting the priority and recency rules.