Update i18n to major version 26

Major version 26 has a breaking change that affects us, this patch
should deal with that.

Author: Arnei

package-lock.json

@@ -19,16 +19,16 @@
     "focus-trap-react": "^12.0.0",
     "formik": "^2.4.9",
     "http-proxy-middleware": "^3.0.5",
-    "i18next": "25.8.11",
+    "i18next": "26.0.7",
     "i18next-browser-languagedetector": "^8.2.1",
-    "i18next-http-backend": "^3.0.5",
+    "i18next-http-backend": "^3.0.6",
     "lodash": "^4.17.23",
     "react": "^19.2.4",
     "react-chartjs-2": "^5.3.1",
     "react-datepicker": "^8.8.0",
     "react-dom": "^19.2.4",
     "react-hotkeys-hook": "^5.2.4",
-    "react-i18next": "16.5.0",
+    "react-i18next": "17.0.4",
     "react-icons": "^5.5.0",
     "react-redux": "^9.2.0",
     "react-router": "^7.13.0",
@@ -67,14 +67,14 @@
     "@types/node": "^25.3.0",
     "@types/react-dom": "^19.2.3",
     "@types/uuid": "^11.0.0",
+    "@vitejs/plugin-react": "^6.0.1",
     "eslint": "^9.39.2",
     "prop-types": "^15.8.1",
     "sass": "^1.97.3",
     "typescript": "^5.9.3",
     "typescript-eslint": "^8.56.0",
     "uuid": "^13.0.0",
     "vite": "^8.0.9",
-    "@vitejs/plugin-react": "^6.0.1",
     "vitest": "^4.0.18"
   }
 }

package.json

@@ -1,4 +1,4 @@
-import i18n from "i18next";
+import i18n, { FormatterModule } from "i18next";
 import { initReactI18next } from "react-i18next";
 
 import HttpBackend, { HttpBackendOptions } from "i18next-http-backend";
@@ -23,7 +23,7 @@ import trTRTrans from "./org/opencastproject/adminui/languages/lang-tr_TR.json";
 import zhCNTrans from "./org/opencastproject/adminui/languages/lang-zh_CN.json";
 import zhTWTrans from "./org/opencastproject/adminui/languages/lang-zh_TW.json";
 import { getCurrentLanguageInformation } from "../utils/utils";
-import { format } from "date-fns/format";
+import { format as dateFnsFormat } from "date-fns/format";
 
 // Assignment of language code to translation file
 // !!! If translation file of a new language is added, please add assignment here, too !!!
@@ -47,29 +47,39 @@ const resources = {
 	"zh-TW": { translation: zhTWTrans },
 } as const;
 
+const myFormatter: FormatterModule = {
+	type: "formatter",
+	init(_services, _i18nextOptions) {},
+	format(value, format, lng, _options) {
+		if (value instanceof Date && format && lng) {
+			return dateFnsFormat(value, format, {
+				locale: getCurrentLanguageInformation(lng)?.dateLocale,
+			});
+		}
+
+		// eslint-disable-next-line @typescript-eslint/no-unsafe-return
+		return value;
+	},
+	add(_name, _fc) { },
+	addCached(_name, _fc) { },
+};
+
 // Configuration of i18next
 i18n
 	.use(HttpBackend)
 	.use(LanguageDetector)
 	.use(initReactI18next)
+	.use(myFormatter)
 	.init<HttpBackendOptions>({
 		resources,
 		fallbackLng: "en-US",
 		debug: false,
 
 		interpolation: {
 			escapeValue: false,
-			format: function (value, formatStr, lng) {
-				if (value instanceof Date && formatStr && lng) {
-					return format(value, formatStr, {
-						locale: getCurrentLanguageInformation(lng)?.dateLocale,
-					});
-				}
-
-				// eslint-disable-next-line @typescript-eslint/no-unsafe-return
-				return value;
-			},
+			alwaysFormat: true,
 		},
+
 		react: {
 			useSuspense: false,
 		},