fix: Locale not correct in root url when accessing help center with custom domain (#9110)

- Ensuring that SwitchLocale concern handles the case of custom domain for portals and set locale according to that

Co-authored-by: Sojan Jose <sojan@pepalo.com>

app/controllers/public/api/v1/portals/base_controller.rb

@@ -47,7 +47,7 @@ class Public::Api::V1::Portals::BaseController < PublicController
     @locale = if article.category.present?
                 article.category.locale
               else
-                'en'
+                article.portal.default_locale
               end
 
     I18n.with_locale(@locale, &)