Recommended language can be set to a language with no content

[Rikdekker]

Bug

The Recommended language (primary/fallback) picker in admin settings lets you choose any Nextcloud language, including ones that have no content. So you can set the recommended language to e.g. Hungarian while your intranet only has content in NL/EN/DE/FR/ES.

This is contradictory:

• The section text promises "Users see content in their own Nextcloud language; if there is none, they are shown the recommended language below." — but if the recommended language is empty, that promise can't be kept.
• The remove-guard protects the recommended language from deletion "so users always have a fallback" — which is meaningless if the recommended language isn't even a content language.

Root cause

• Frontend: the picker iterates allAvailableLanguages (all NC languages) instead of the languages-with-content set (src/components/AdminSettings.vue).
• Backend: LanguageService::setPrimaryLanguage() only validates isLanguageAvailable() (is it a known NC language), not "does it have content".

Expected

The recommended language should be chosen from the languages that have content (plus English as the universal fallback, since it's the source language and always resolvable). Setting a recommended language without content should not be possible — via the UI or the API.

Also handle

• If the admin removes the language that is currently recommended from the content set, the recommended language should fall back sensibly (e.g. to English).

Impact

Not a crash — the runtime fallback notice lists the languages-with-content and links to personal settings; it does not silently send users to the empty recommended language. So the impact is misleading admin UX + an illogical, unpreventable state rather than a broken end-user experience.

Fix will ship in 1.8.1.

[Rikdekker]

Fixed on main (commit fbb86fa) — will ship in 1.8.1.

• The Recommended language picker now lists only languages that have content (plus English as the universal fallback), instead of all Nextcloud languages.
• LanguageController::setPrimary rejects a code that is not en and not among the content languages with HTTP 400, so the illogical state can't be set via the API either.

Verified on a test instance: setting a non-content language (hu) → 400 ("The recommended language must be a language that has content"), en and a content language (de) → 200; the picker now lists only the content languages (de/en/es/fr/nl), no empty ones. removeLanguage already blocked removing the current recommended language, so that path needed no change.

[Rikdekker]

Fixed in 1.8.1 (just released — https://github.com/nextcloud/IntraVox/releases/tag/v1.8.1).

The recommended (fallback) language picker now only offers languages that actually have content (plus English, the universal source/fallback), and the backend rejects setting the recommended language to one without content (POST /api/languages/primary returns 400). So an admin can no longer point the fallback at an empty language, which used to leave users whose own language has no pages staring at a blank intranet.