Update javalin-maven-java example to match gradle-kotlin module (fixes #241)

[Boda65665]

Summary

This PR updates the javalin-maven-java example, which was outdated and failed to compile under modern JDKs, as described in issue #241.

Changes

• Updated Javalin to 6.7.0
• Updated Javalin OpenAPI plugins to 6.7.0-2
• Switched compiler target to JDK 17
• Added missing dependencies:
  • org.projectlombok:lombok:1.18.28
  • jakarta.validation:jakarta.validation-api:2.0.2
  • org.mongodb:bson:4.9.1
• Fixed NoSuchFieldError in openapi-annotation-processor
• Replaced Lombok RecordEntity with proper Java record
• Verified that /api/openapi.json and /swagger render correctly

Testing

✅ Successfully ran JavalinTest with OpenAPI, Swagger, and ReDoc UI
✅ Confirmed valid OpenAPI 3.0.3 spec generation
✅ Compatible with Maven + JDK 17

Closes

Fixes #241