上映会改修 (#302) (#357)

Reviewed-on: http://git.miteruzo.com/miteruzo/btrc-hub/pulls/357
Co-authored-by: miteruzo <miteruzo@naver.com>
Co-committed-by: miteruzo <miteruzo@naver.com>

backend/app/models/theatre_programme.rb

@@ -0,0 +1,6 @@
+class TheatreProgramme < ApplicationRecord
+  self.primary_key = :theatre_id, :position
+
+  belongs_to :theatre
+  belongs_to :post
+end