3.18.9
(fix): Fix wire test generation to use OptionalNullable when collapse-optional-nullable is enabled. Wire tests now correctly generate OptionalNullable.absent() and OptionalNullable.of() instead of Optional.empty() and Optional.of() for optional request bodies and method arguments when collapse-optional-nullable: true is configured. This includes support for nested optional/nullable types which collapse into a single OptionalNullable<T>.
