Fix language code detection for more than 2 letters codes

src/app/services/internationalisation.service.ts

@@ -55,11 +55,12 @@ export class I18nService extends Observable implements Observer {
     /**
      * Defines the current language code from its ISO 639-1 code (2 characters) or locale code
      * (ex: "fr", "en", "fr_FR", "en-US")
-     * @see this.languageCodeFromLocaleCode()
      *
      * @param code ISO 639-1 language code
      */
     public async setLanguage(code: string) {
+        // ensure 2-letter language code
+        code = code.substring(0, 2);
         // is language supported ?
         if (! Object.keys(this._availableLanguages).includes(code)) {
             throw new Error(`LANGUAGE_UNSUPPORTED "${code}"`);