Add language customization flag (#7374)

This allows you to customize any string (that has a translation) or add your own translations.

src/node/i18n/index.ts

@@ -1,3 +1,4 @@
+import { promises as fs } from "fs"
 import i18next, { init } from "i18next"
 import * as en from "./locales/en.json"
 import * as ja from "./locales/ja.json"
@@ -5,29 +6,54 @@ import * as th from "./locales/th.json"
 import * as ur from "./locales/ur.json"
 import * as zhCn from "./locales/zh-cn.json"
 
+const defaultResources = {
+  en: {
+    translation: en,
+  },
+  "zh-cn": {
+    translation: zhCn,
+  },
+  th: {
+    translation: th,
+  },
+  ja: {
+    translation: ja,
+  },
+  ur: {
+    translation: ur,
+  },
+}
+
+export async function loadCustomStrings(filePath: string): Promise<void> {
+  try {
+    // Read custom strings from file path only
+    const fileContent = await fs.readFile(filePath, "utf8")
+    const customStringsData = JSON.parse(fileContent)
+
+    // User-provided strings override all languages.
+    Object.keys(defaultResources).forEach((locale) => {
+      i18next.addResourceBundle(locale, "translation", customStringsData)
+    })
+  } catch (error) {
+    if (error && typeof error === "object" && "code" in error && error.code === "ENOENT") {
+      throw new Error(`Custom strings file not found: ${filePath}\nPlease ensure the file exists and is readable.`)
+    } else if (error instanceof SyntaxError) {
+      throw new Error(`Invalid JSON in custom strings file: ${filePath}\n${error.message}`)
+    } else {
+      throw new Error(
+        `Failed to load custom strings from ${filePath}: ${error instanceof Error ? error.message : String(error)}`,
+      )
+    }
+  }
+}
+
 init({
   lng: "en",
   fallbackLng: "en", // language to use if translations in user language are not available.
   returnNull: false,
   lowerCaseLng: true,
   debug: process.env.NODE_ENV === "development",
-  resources: {
-    en: {
-      translation: en,
-    },
-    "zh-cn": {
-      translation: zhCn,
-    },
-    th: {
-      translation: th,
-    },
-    ja: {
-      translation: ja,
-    },
-    ur: {
-      translation: ur,
-    },
-  },
+  resources: defaultResources,
 })
 
 export default i18next