[Epic] Refactor oneCoupon: EDA + DDD + Clean Architecture (Kafka, Temporal)

[Rurutia1027]

[Epic] Refactor oneCoupon: EDA + DDD + Clean Architecture (Kafka, Temporal)

Goal

Evolve Promption-Engine from layered Spring microservices (shared DB, duplicated RocketMQ glue) into an event-driven, domain-centric platform:

Pillar	Target
Clean Architecture	Domain at the center; Kafka, JPA, Redis, Temporal as adapters behind ports
DDD	Bounded contexts, aggregates, domain events -- business rules in domain-core, not *ServiceImpl
EDA	Kafka + outbox + Avro contracts; sagas for cross-service flows; idempotent consumers

Why

• Shared MySQL + duplicated *DO / MQ templates block true service boundaries.
• RocketMQ delay/DLQ does not map 1:1 to strict EDA - migrate to Kafka + Temporal + retry/DLT topics

Scope (phased)

1. Foundation — common-domain, infrastructure/{outbox,saga,messaging-kafka,event-contract}, ArchUnit rules
2. Pilot slice — Merchant coupon task → Temporal schedule → outbox → Kafka → Distribution (replace XXL-Job + RocketMQ on this path)
3. Expand — Engine (redeem, order saga), settlement projections, search (domain events vs Canal)
4. Retire — RocketMQ dependencies, per-module send templates, shared-table coupling

Out of Scope (for now)

• Full DB-per-service cutover for all contexts
• Production multi-region / full K8s platform

Done when

• One vertical slice runs on ports + outbox + Kafka with Temporal for scheduling
• domain-core has no Kafka / JPA / Web dependencies (ArchUnit green)
• P0 consumers have retry + DLT and idempotent processing
• Refactor design docs updated with pilot outcomes