Export multilingual hall names

app/views/api/halls/index.jbuilder

@@ -1,5 +1,9 @@
 @halls.each do |hall|
   json.set! hall.id do
-    json.extract! hall, :name
+    json.name do
+      hall.translations.each do |translation|
+        json.set! translation.locale, translation.name
+      end
+    end
   end
 end