Like CookieLocaleResolver, LocaleChangeInterceptor parses both locale formats by default now. Since it does not need to render the locale, its languageTagCompliant property is not relevant anymore at all.
The parseLocale method in StringUtils validates the locale value now and turns an empty locale into null, compatible with parseLocaleString behavior and in particular aligned with web locale parsing needs.
Issue: SPR-16700
Issue: SPR-16651