Add OpenAPI 3.0.x support and improve test coverage

[FrancescoPanico]

Summary

This pull request adds support for OpenAPI 3.0.x while preserving the existing Swagger 2.0 behavior.

Changes

• Added support for parsing and comparing OpenAPI 3.0.x specifications.
• Introduced the io.swagger.parser.v3:swagger-parser:2.1.22 dependency to parse OpenAPI 3.0.x definitions.
• Kept all existing test cases to ensure backward compatibility.
• Added a new set of tests specifically targeting OpenAPI 3.0.x YAML specifications.
• Focused the new test cases on response definitions, as this area differs significantly from Swagger 2.0 and required dedicated validation.
• Added a Maven code coverage plugin to help measure and monitor test coverage.

Testing

• All existing tests continue to pass unchanged.
• New OpenAPI 3.0.x YAML tests validate the new functionality while preserving Swagger 2.0 compatibility.

Any feedback is welcome.