フォームのバリデーションとニコ連携の画面変更 (#090) (#355)

Reviewed-on: http://git.miteruzo.com/miteruzo/btrc-hub/pulls/355
Co-authored-by: miteruzo <miteruzo@naver.com>
Co-committed-by: miteruzo <miteruzo@naver.com>

backend/app/controllers/theatre_comments_controller.rb

@@ -15,7 +15,7 @@ class TheatreCommentsController < ApplicationController
     return head :unauthorized unless current_user
 
     content = params[:content]
-    return head :unprocessable_entity if content.blank?
+    return render_unprocessable_entity('本文は必須です．', field: :content) if content.blank?
 
     theatre = Theatre.find_by(id: params[:theatre_id])
     return head :not_found unless theatre