feat(admin-*,dashboard): add dashboard i18n extensions (#13763)

* virtual i18n module

* changeset

* fallback ns

fallback to the default "translation" ns if the key isnt found. Allows to use a single "useTranslation("customNs")" hook for both custom and medusa-provided keys

* simplify merges

* optional for backward compat

* fix HMR

* fix generated deepMerge

* test

packages/admin/dashboard/src/components/utilities/i18n/i18n.tsx

@@ -3,12 +3,16 @@ import LanguageDetector from "i18next-browser-languagedetector"
 import { initReactI18next } from "react-i18next"
 
 import { defaultI18nOptions } from "../../../i18n/config"
+import { useExtension } from "../../../providers/extension-provider"
 
 export const I18n = () => {
+  const { getI18nResources } = useExtension()
+
   if (i18n.isInitialized) {
     return null
   }
 
+  const resources = getI18nResources()
   i18n
     .use(
       new LanguageDetector(null, {
@@ -17,7 +21,11 @@ export const I18n = () => {
       })
     )
     .use(initReactI18next)
-    .init(defaultI18nOptions)
+    .init({
+      ...defaultI18nOptions,
+      resources,
+      supportedLngs: Object.keys(resources),
+    })
 
   return null
 }