Add active_language controller and cookie storage

spec/factories/languages.rb

@@ -1,5 +1,9 @@
 FactoryBot.define do
   factory :language do
-    name { "MyString" }
+    sequence(:name) { |n| "MyString#{n.to_s}" }
+  end
+
+  factory :language_english, class: :language do
+    name { "English" }
   end
 end