$ curl -s -i -X POST localhost:8080/contact-record \
     -H 'Content-Type: application/json' \
     -d '{"email":"spammy@email.com","message":"This is spam."}'

HTTP status: 400
Body: '' (empty!)

# The record parameter has no BindingResult to collect field errors into, unlike
# ContactController#submitContactForm's class-based, BindingResult-carrying signature.
# A failing constraint throws MethodArgumentNotValidException instead, and Boot 4.1's
# default handling for it returns an EMPTY body when the request has no Accept header
# asking for a structured error. See the next transcript for what changes with one.