sequenceDiagram
                participant Partner as 파트너
                participant LinkPay as EXIMLink API
                participant Customer as 고객
            
                Partner->>LinkPay: 1. 토큰 발급 (apiKey)
                LinkPay-->>Partner: Access Token
                Partner->>LinkPay: 2. 인보이스 생성 (Token)
                LinkPay-->>Partner: 결제 링크 (paymentUrl)
                LinkPay->>Customer: 이메일/SMS 발송
                Customer->>LinkPay: 3. 결제 진행
                LinkPay->>Partner: 4. 웹훅 발송 (PAYMENT_COMPLETED)