CreateTranscriptionBlockDTO and UpdateTranscriptionBlockDTO gain a
List<PersonMention> mentionedPersons field. @Valid is on the field itself,
not just on the controller method, so JSR-303 recurses into the list
elements when the controller boundary calls @Valid on the @RequestBody. The
collection defaults to an empty ArrayList via @Builder.Default; existing
constructor call sites in TranscriptionServiceTest are extended with
List.of() to match the new @AllArgsConstructor signature.
The controller-side @Valid wiring lands in the next commit alongside the
length-201 validation test.
Refs #362
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
80ddfb47ac