fix: using app locale for citations

* app was using navigator.language which is always
* browser setting. The change enables using localization
* based on app settings and using translated strigns that exist in
* citeproc library

Author: Ducica

invenio_app_rdm/theme/assets/semantic-ui/js/invenio_app_rdm/landing_page/RecordCitationField.js

@@ -58,7 +58,13 @@ export class RecordCitationField extends Component {
 
   fetchCitation = async (recordLinks, style, includeDeleted) => {
     const includeDeletedParam = includeDeleted === true ? "&include_deleted=1" : "";
-    const url = `${recordLinks.self}?locale=${navigator.language}&style=${style}${includeDeletedParam}`;
+    const navLang = (navigator.language || "").toLowerCase();
+    const uiLang = (i18next.language || "").toLowerCase();
+    const citationLocale =
+      uiLang && navLang.startsWith(uiLang)
+        ? navigator.language
+        : i18next.language || navigator.language;
+    const url = `${recordLinks.self}?locale=${citationLocale}&style=${style}${includeDeletedParam}`;
     return await http.get(url, {
       headers: {
         Accept: "text/x-bibliography",