Payment order models — requests, responses, and enums

[rammrain]

Summary

Define all DTOs and enums needed for the payment order API.

Requirements

Enums

• PaymentStatus: PENDING, PAID, VOIDED, PARTIALLY_REFUNDED, REFUNDED, CANCELED, ABANDONED, DECLINED, SETTLED, AUTHORIZED
• PaymentMethodType: paymentInitiation, cardPayments, bnpl, hirePurchase
• Currency: EUR, PLN (at minimum)
• Locale: DE, EN, ET, FI, LT, LV, PL, RU

Request DTOs

• CreateOrderRequest: merchant reference, amount, currency, payment method, bank code, locale, return URL, notification URL, billing address, line items
• LineItem: description, quantity, unit price
• Address: billing address fields

Response DTOs

• CreateOrderResponse: payment URL, order UUID
• OrderStatusResponse: order UUID, payment status, merchant reference, grand total, payment method type, payment intents
• PaymentIntent: intent UUID, status, payment method type, amount, service fee

General

• Null-safe — clearly indicate nullable fields
• Jackson annotations for JSON serialization/deserialization

Refs

• initial-docs/project1.md — order payload fields
• initial-docs/project2.md — line items, statuses, currencies, locales, payment method types
• initial-docs/project3.md — order response structure, payment intents

Testing

Unit tests for: serialization/deserialization round-trips, enum coverage, builder/constructor validation, null handling. Target near-perfect coverage.