多言語化の基盤作り (#55) (#421)

Reviewed-on: #421
Co-authored-by: miteruzo <miteruzo@naver.com>

backend/app/models/language.rb

@@ -0,0 +1,5 @@
+class Language < ApplicationRecord
+  has_many :locales, foreign_key: :language_code, primary_key: :code
+
+  enum :code, ja: 'ja'
+end