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Adds the framework's event bus, the second cross-cutting service (after auth) that PBCs and plug-ins both consume. Implements the transactional outbox pattern from the architecture spec section 9 — events are written to the database in the same transaction as the publisher's domain change, so a publish followed by a rollback never escapes. This is the seam where a future Kafka/NATS bridge plugs in WITHOUT touching any PBC code. What landed: * New `platform/platform-events/` module: - `EventOutboxEntry` JPA entity backed by `platform__event_outbox` (id, event_id, topic, aggregate_type, aggregate_id, payload jsonb, status, attempts, last_error, occurred_at, dispatched_at, version). Status enum: PENDING / DISPATCHED / FAILED. - `EventOutboxRepository` Spring Data JPA repo with a pessimistic SELECT FOR UPDATE query for poller dispatch. - `ListenerRegistry` — in-memory subscription holder, indexed both by event class (Class.isInstance) and by topic string. Supports a `**` wildcard for the platform's audit subscriber. Backed by CopyOnWriteArrayList so dispatch is lock-free. - `EventBusImpl` — implements the api.v1 EventBus. publish() writes the outbox row AND synchronously delivers to in-process listeners in the SAME transaction. Marked Propagation.MANDATORY so the bus refuses to publish outside an existing transaction (preventing publish-and-rollback leaks). Listener exceptions are caught and logged; the outbox row still commits. - `OutboxPoller` — Spring @Scheduled component that runs every 5s, drains PENDING / FAILED rows under a pessimistic lock, marks them DISPATCHED. v0.5 has no real external dispatcher — the poller is the seam where Kafka/NATS plugs in later. - `EventBusConfiguration` — @EnableScheduling so the poller actually runs. Lives in this module so the seam activates automatically when platform-events is on the classpath. - `EventAuditLogSubscriber` — wildcard subscriber that logs every event at INFO. Demo proof that the bus works end-to-end. Future versions replace it with a real audit log writer. * `platform__event_outbox` Liquibase changeset (platform-events-001): table + unique index on event_id + index on (status, created_at) + index on topic. * DefaultPluginContext.eventBus is no longer a stub that throws — it's now the real EventBus injected by VibeErpPluginManager. Plug-ins can publish and subscribe via the api.v1 surface. Note: subscriptions are NOT auto-scoped to the plug-in lifecycle in v0.5; a plug-in that wants its subscriptions removed on stop() must call subscription.close() explicitly. Auto-scoping lands when per-plug-in Spring child contexts ship. * pbc-identity now publishes `UserCreatedEvent` after a successful UserService.create(). The event class is internal to pbc-identity (not in api.v1) — other PBCs subscribe by topic string (`identity.user.created`), not by class. This is the right tradeoff: string topics are stable across plug-in classloaders, class equality is not, and adding every event class to api.v1 would be perpetual surface-area bloat. Tests: 13 new unit tests (9 EventBusImplTest + 4 OutboxPollerTest) plus 2 new UserServiceTest cases that verify the publish happens on the happy path and does NOT happen when create() rejects a duplicate. Total now 76 unit tests across the framework, all green. End-to-end smoke test against fresh Postgres with the plug-in loaded (everything green): EventAuditLogSubscriber subscribed to ** at boot Outbox empty before any user create ✓ POST /api/v1/auth/login → 200 POST /api/v1/identity/users (create alice) → 201 Outbox row appears with topic=identity.user.created, status=PENDING immediately after create ✓ EventAuditLogSubscriber log line fires synchronously inside the create transaction ✓ POST /api/v1/identity/users (create bob) → 201 Wait 8s (one OutboxPoller cycle) Both outbox rows now DISPATCHED, dispatched_at set ✓ Existing PBCs still work: GET /api/v1/identity/users → 3 users ✓ GET /api/v1/catalog/uoms → 15 UoMs ✓ Plug-in still works: GET /api/v1/plugins/printing-shop/ping → 200 ✓ The most important assertion is the synchronous audit log line appearing on the same thread as the user creation request. That proves the entire chain — UserService.create() → eventBus.publish() → EventBusImpl writes outbox row → ListenerRegistry.deliver() finds wildcard subscriber → EventAuditLogSubscriber.handle() logs — runs end-to-end inside the publisher's transaction. The poller flipping PENDING → DISPATCHED 5s later proves the outbox + poller seam works without any external dispatcher. Bug encountered and fixed during the smoke test: • EventBusImplTest used `ObjectMapper().registerKotlinModule()` which doesn't pick up jackson-datatype-jsr310. Production code uses Spring Boot's auto-configured ObjectMapper which already has jsr310 because spring-boot-starter-web is on the classpath of distribution. The test setup was the only place using a bare mapper. Fixed by switching to `findAndRegisterModules()` AND by adding jackson-datatype-jsr310 as an explicit implementation dependency of platform-events (so future modules that depend on the bus without bringing web in still get Instant serialization). What is explicitly NOT in this chunk: • External dispatcher (Kafka/NATS bridge) — the poller is a no-op that just marks rows DISPATCHED. The seam exists; the dispatcher is a future P1.7.b unit. • Exponential backoff on FAILED rows — every cycle re-attempts. Real backoff lands when there's a real dispatcher to fail. • Dead-letter queue — same. • Per-plug-in subscription auto-scoping — plug-ins must close() explicitly today. • Async / fire-and-forget publish — synchronous in-process only.
