feat: Quarkus support for the Process Engine Worker (#265)

[Hafflgav]

Closes #265

Summary

Extracts a framework-independent core from the Spring Boot starter, keeps the starter backward compatible and adds a Quarkus extension with build-time worker discovery. JPA-based idempotency is now available for both frameworks.

Module layout

Module	Artifact	Notes
core/	process-engine-worker-core	Kotlin, no Spring/Quarkus dependency: annotations, ProcessEngineWorkerRegistrar, resolvers, exceptions, metrics, idempotency logic, SPIs TransactionalExecutor / AfterCommitHook / TransactionalMethodDetector
spring-boot-starter/	process-engine-worker-spring-boot-starter	Thin layer over core; same class names, constructor, .imports and properties
idempotency-registry-jpa/	process-engine-worker-idempotency-registry-jpa	Framework-free JPA registry (entity/converter moved with unchanged FQCNs and schema, EntityManagerJpaIdempotencyRegistry, pluggable Java/Jackson serializer)
spring-boot-idempotency-registry-jpa/	unchanged	Now on top of the shared JPA module
quarkus/runtime + quarkus/deployment	process-engine-worker-quarkus (+ -deployment)	Quarkus extension (runtime Kotlin, deployment Java)

Quarkus extension

• Jandex discovery of @ProcessEngineWorker methods; worker classes need no scope annotation (auto @Singleton, unremovable).
• Registration in a RUNTIME_INIT recorder step (ServiceStartBuildItem), i.e. before any StartupEvent observer and therefore before the C8 Quarkus adapter subscribes its job workers.
• Build-time validation: non-public/static/abstract worker methods, workers exposed via @Produces, duplicate topics (per tenant), Kotlin dual constructors, vetoed classes, topic/value conflicts.
• Optional integrations detected at build time: JTA transactions (quarkus-narayana-jta), Micrometer metrics, JPA idempotency (quarkus-hibernate-orm + the JPA module).
• All provided beans are @DefaultBeans, replaceable by a user @Produces.
• Config keys identical to Spring: dev.bpm-crafters.process-api.worker.{enabled,complete-tasks-before-commit,remove-task-result-on-completion,tenant-id}.
• Native image: worker classes, @Variable types and converters are registered for reflection.

Compatibility (Spring Boot)

No source changes required for existing projects (examples/ and itest/ build unchanged). Documented deltas:

• @AliasFor removed from @ProcessEngineWorker / @Variable; topic/value and name/value alias semantics are reproduced by the core.
• ProcessEngineStarterRegistrar.TaskHandlerWithResult / FailureRetry moved to ProcessEngineWorkerRegistrar (core).
• registerProcessWorkers deprecated (it was never evaluated; enabled is the switch).

Documentation

README reworked (framework matrix, Quarkus sample, links), docs/process-engine-worker.md framework-neutral with corrected configuration, new docs/spring-boot.md and docs/quarkus.md, updated docs/idempotency.md and docs/process-deployment.md.

Companion step: add docs/spring-boot.md and docs/quarkus.md to the nav of process-engine-api-docs.

Out of scope / follow-ups

• Quarkus example app and a real-engine Quarkus integration test: after process-engine-adapter-camunda-platform-c8-quarkus is released.
• Quarkus auto-deployment of BPMN/DMN resources.
• Reactive worker return types.

Test plan

• ./mvnw clean verify -T4 (CI command): all modules green, 167 tests (core 67, Spring 11, JPA 16, Quarkus runtime 14, Quarkus deployment 42, Spring itests 17 against Camunda 7 + Postgres via Testcontainers)
• -Prelease packaging: sources + javadoc jars for all new modules, extension descriptor validation passes
• Failsafe now also runs the nested IdempotencyITest variants (previously never executed); registrar itests wait up to 60s to tolerate the external task client backoff under parallel load
• Manual smoke test against the (unreleased) C8 Quarkus adapter once it is available

🤖 Generated with Claude Code