Lets the emails speak the instance's language from the same catalogs as the interface. A template passes each message as a descriptor holding its id and its English, as i18n._({ id: "email.reset.title", message: "Reset your password" }), or one of shared/digest-messages.ts, which a page says too. lingui extract reads them into locales/<lang>.po beside the interface's messages, and lingui compile turns the catalogs into the locales/<lang>.mjs imported here, failing when a language lacks one. The ids are named rather than hashed from the English, since the server runs no Lingui macro.