PR checklist

• Read the contribution guidelines.
• Run the following to build the project and update samples:

  ./mvnw clean package || exit
  ./bin/generate-samples.sh ./bin/configs/*.yaml || exit
  ./bin/utils/export_docs_generators.sh || exit
  

  (For Windows users, please run the script in WSL)
  Commit all changed files.
  This is important, as CI jobs will verify all generator outputs of your HEAD commit as it would merge with master.
  These must match the expectations made by your contribution.
  You may regenerate an individual generator by passing the relevant config(s) as an argument to the script, for example ./bin/generate-samples.sh bin/configs/java*.
  IMPORTANT: Do NOT purge/delete any folders/files (e.g. tests) when regenerating the samples as manually written tests may be removed.
• If your PR is targeting a particular programming language, @mention the technical committee members, so they are more likely to review the pull request.

Summary by cubic

Adds useOneOfInterfaces, useSealed, and useRecords to jaxrs-spec to generate oneOf interfaces, optional sealed hierarchies, and record implementations; updates discriminator mapping and accessor signatures so polymorphic serialization works and record outputs compile cleanly.

• New Features

  • useOneOfInterfaces: oneOf schemas render as Java interfaces; subtypes implement them; interface carries typed discriminator getter and Jackson type annotations via oneof_interface template.
  • useSealed: marks the interface sealed and lists permitted subtypes; implementing classes become final; POM switches to Java 17.
  • useRecords: eligible implementors of a generated oneOf interface render as Java records (no parent, no additionalProperties); the interface declares the discriminator accessor in record style so records satisfy it; records are not forced final; POM switches to Java 17. Independent of useSealed.
  • Routing and templates updated (model.mustache, sealed/permits helpers, record.mustache); new sample/config (jaxrs-spec-records) added and included in the JDK17 samples workflow.

• Bug Fixes

  • Resolve the discriminator property type and @JsonTypeName for subtypes from the oneOf interface’s mapped children when the parent is an interface, avoiding String fallback and ensuring correct enum types.
  • Tests added for interface-only, sealed, and record scenarios to verify mappings and method signatures.

^{Written for commit 940a93b. Summary will update on new commits.}