- Replace InstitutionContractExtensionPaymentResponse with InstitutionContractDiscountResponse in discount-related methods and endpoints
- Update request and response models to include OneMonthAmount, Obligation, and improved discount fields
- Adjust method signatures and controller actions to use new response types
- Refactor discount calculation logic to support new structure and ensure correct plan updates for both installment and one-time payments
- Improve naming consistency for discount percentage fields