Companion code for "Global Exception Handling with ProblemDetail (RFC 9457)
in Spring Boot 4". Thirteen failures under five handling setups (Boot
defaults, the Boot flag, a ResponseEntityExceptionHandler advice, advice
plus an ErrorController, a catch-all ordered first), validation errors,
i18n, content negotiation, Security's 401/403, silent 500s and decoding
on the client. 16 tests pin the behaviour.
Co-Authored-By: Claude Opus 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01C3TETMrqVUWeFkNtz3Jbo3
