nginx ignition has ParseAcceptLanguage `_` separator bypass that enables ~75x CPU amplification via Accept-Language header in i18nMiddleware

Summary The gin i18n middleware in nginx-ignition's API server runs in front of every HTTP request and calls golang.org/x/text/language.ParseAcceptLanguage on the raw Accept-Language header without imposing any size or shape filter. The underlying parser has quadratic-time behaviour on long lists...