Summary

Prepare the 1.6.0 release with four user-facing OpenAPI DSL improvements:

• preserve insertion order when serializing OpenAPI documents to strings and files;
• support every OpenAPI 3.0 component category with matching reference helpers;
• register root and transitively referenced schemas automatically without overwriting explicit customizations;
• optionally infer required properties from Kotlin constructor nullability while preserving annotations, default behavior, and build isolation;
• bump the published Gradle project version from 1.5.0 to 1.6.0.

Compatibility

• OpenAPI.asJson() keeps its existing JSONObject return type and intentionally unspecified key order.
• The existing openapiDsl { ... } JVM signature remains available.
• Kotlin required-property inference is opt-in and disabled by default.
• Explicit component customizations and Swagger requiredMode annotations take precedence over inferred values.

Verification

• ./gradlew test --rerun-tasks --console=plain
• 45 tests, 0 failures, 0 errors, 0 skipped
• nested, parallel, exception-cleanup, and same-model sequential schema builds covered
• all changed code files remain below 500 lines
• Gradle configuration resolves the publication version as 1.6.0

Issues

Closes #146
Closes #88
Closes #245
Closes #147