feat(dashboard, medusa) add metadata to pages (#9433)

**WIP**
- add metadata component and edit route to missing pages
- fix API issues around metadata in certain domains

---

FIXES CC-554

packages/medusa/src/api/admin/sales-channels/query-config.ts

@@ -6,6 +6,7 @@ export const defaultAdminSalesChannelFields = [
   "created_at",
   "updated_at",
   "deleted_at",
+  "metadata",
 ]
 
 export const retrieveTransformQueryConfig = {

packages/medusa/src/api/admin/users/validators.ts

@@ -37,4 +37,5 @@ export const AdminUpdateUser = z.object({
   first_name: z.string().nullish(),
   last_name: z.string().nullish(),
   avatar_url: z.string().nullish(),
+  metadata: z.record(z.unknown()).nullish().optional(),
 })