[jaxrs-spec] useRecords pojo parity + records samples for every library in CI

[Ignacio-Vidal]

Draft — stacked on #24188.
GitHub cannot target a fork branch as a PR base, so this targets master and
its diff therefore also contains #24188's commit ([jaxrs-spec] Support useRecords). Review only the two commits on top of it:

• [jaxrs-spec] Bring useRecords records to pojo feature parity
• [jaxrs-spec] Add records samples for every library and build them in CI

Once #24188 merges, this will be rebased onto master and the diff will
reduce to those two commits. Marked ready for review at that point.

1. Bring useRecords records to pojo feature parity

Records emitted for oneOf-interface implementations were missing behaviour the
pojo template already had. Each feature is gated on a vendor extension computed
in postProcessAllModels, so records without the relevant properties are
unaffected:

extension	what it adds
x-jaxrs-record-has-defaults	compact canonical constructor applying defaults on null (scalar, enum, container, and JsonNullable → of(default) / undefined())
x-jaxrs-record-has-byte-array	explicit equals/hashCode using Arrays.*, since the implicit record versions compare arrays by reference
x-jaxrs-record-has-password	explicit toString masking format: password values

Also: doc annotations on record components, JsonNullable<T> component types,
and generateBuilders support via a flat static nested builder (records cannot
use the pojo's abstract builder hierarchy).

useRecords + withXml now throws IllegalArgumentException rather than
generating something that cannot work.

2. Samples for every jaxrs-spec library, compiled in CI

useRecords lives in the shared model/record templates, so it applies to all
five libraries — but only the default one had a sample. This adds one per
library (helidon, kumuluzee, openliberty, quarkus, thorntail) and registers all
five in the JDK17 samples workflow, so they are compiled on every push and PR.

Two fixes were needed to make them compile:

• Library poms hardcoded Java 1.8 (helidon: 11). Every library overrides
  pom.mustache, so none inherited the base template's useSealed/useRecords
  → 17 gating. Applied the same gating to all five.

• record.mustache imported JsonNullable unconditionally. The import is
  already contributed through the imports block for models that use it, so
  records with a nullable component carried a duplicate import, and records
  without one carried an unused import that fails to compile on libraries
  whose pom omits jackson-databind-nullable.

kumuluzee, openliberty and thorntail set openApiNullable=false in their sample
config. Their poms omit jackson-databind-nullable while the pojo template
imports JsonNullable whenever openApiNullable is on. That is pre-existing and
unrelated to records — it reproduces with no records flags set at all — so it is
worked around here rather than fixed in this PR.

Verification

• 158 JavaJAXRSSpecServerCodegenTest, 730 Java codegen tests — all green
• All six records samples plus jaxrs-spec-sealed build under JDK 17
• Docs regenerate with no diff

Two unrelated pre-existing bugs found while testing this are split into their
own PRs rather than bundled here:

• microprofile client emitting equalsNullable calls whose helpers are never defined
• jaxrs-spec pojo builder declaring the raw type for a JsonNullable property

---

Summary by cubic

Brings useRecords in jaxrs-spec to full parity with POJOs for oneOf interface implementations and adds record samples for every library, compiled in CI. Also gates all jaxrs-spec poms to JDK 17 when useRecords/useSealed are enabled and documents the new option.

• New Features
  • Records are emitted only for oneOf implementors when useOneOfInterfaces=true, useSealed=true, and useRecords=true (JDK 17). All other models remain classes.
  • POJO parity for records: constructor-applied defaults (scalars, enums, containers), JsonNullable<T> components default to undefined(), content-based equals/hashCode for byte[], masked toString for password fields, doc annotations on components, and a flat generateBuilders builder.
  • OneOf interface uses record-style accessor for the discriminator only when records are emitted; otherwise getters remain unchanged.
  • useRecords cannot be combined with withXml (throws IllegalArgumentException).
  • Samples: added record samples for default, helidon, kumuluzee, openliberty, quarkus, and thorntail, and included them in the JDK 17 samples workflow. Fixed duplicate JsonNullable import in record.mustache. Library pom.mustache files now set source/target to 17 when useRecords or useSealed; docs updated to include useRecords.

^{Written for commit 20a862f. Summary will update on new commits.}