Update chapter04.adoc about MicroProfile OpenAPI 4.1 with the latest features from OpenAPI 3.0

[ttelang]

This PR contains is for updating Chapter 04 of the official MicroProfile 7.1 API Tutorial with the coverage the latest feature and enhancements in MicroProfile OpenAPI 4.1.

This chapter provides detailed coverage of OpenAPI Specification integration with Jakarta RESTful Web Services, focusing on annotation-driven API documentation generation.

Topics Updated

• Swagger UI Integration: Interactive API exploration and testing
• Complete Code Examples: Working code examples with explanations
• MicroProfile OpenAPI 4.1 New Features: Detailed coverage of all new features in version 4.1:
  • OpenAPI v3.1 Specification Support
    • JSON Schema 2020-12 alignment
    • Improved nullable type handling with type arrays
    • Enhanced schema composition (oneOf, anyOf, allOf)
    • Optional<T> support for nullable fields
  • Java Records Support
    • Native documentation generation for Java records
  • Enhanced Annotation Type Safety
    • @Target meta-annotation improvements
    • Compile-time validation
    • IDE integration benefits
  • JSON Schema Dialect Support
    • Default vs. full JSON Schema 2020-12 dialects
    • Programmatic dialect specification
    • CustomModelReader implementation
  • Extensible Interface Methods
    • New hasExtension() and getExtension() convenience methods
    • Vendor extensions documentation
    • ExtensionFilter implementation for dynamic documentation
  • Asynchronous Operations with Callbacks
    • Webhook-style API documentation
    • @Callback and @CallbackOperation usage
  • Comprehensive Security Schemes
    • API Key authentication
    • JWT Bearer token authentication
    • OAuth2 with authorization code flow
    • Security requirement application at operation and class levels

I would be sharing another PR for the associated code changes in next few days.