Generated @Serializable classes with date-time (kotlin.time.Instant) fields fail to compile (missing serializer)

[halotukozak]

Description

date-time schema fields are mapped to kotlin.time.Instant, but no serializer is generated or registered for it. Generated @Serializable data classes with a date-time property fail to compile:

e: .../model/Pet.kt:27:25 Serializer has not been found for type 'Instant?'.
To use context serializer as fallback, explicitly annotate type or property with @Contextual

kotlinx-serialization (1.8.1) has no built-in serializer for the new stdlib kotlin.time.Instant. UUID fields already get a generated UuidSerializer + @UseSerializers; date-time needs equivalent handling.

How to reproduce

Generate a client from a spec with a property { type: string, format: date-time } inside a component schema, then compile the output.

Acceptance criteria

• @Serializable classes with date-time properties compile
• A serializer for kotlin.time.Instant is generated/registered (mirroring the UUID approach) or another supported mapping is chosen
• Covered by the compilation test (re-add a date-time field to the feature-rich spec in JustworksPluginFunctionalTest)

Discovered in

PR #88 (compilation test for #46) — the date-time field was omitted from the test spec to keep that PR focused.