Somewhere in i18next there is an assignment `ctx.lng=someLang` that
leaks across requests that share the same `ctx` object for calls like
`req.i18n.translate('locale', ctx)`.
This somewhere is likely here:
6cc8917ed5/src/i18next.translate.js (L338)
GitOrigin-RevId: b05f62fa59a6ffa59724108fbcc68cc7a67cfd8f