post_tags の論理削除と履歴管理を廃止 (#411) (#417)

Reviewed-on: #417
Co-authored-by: miteruzo <miteruzo@naver.com>

backend/app/services/youtube/sync.rb

@@ -103,7 +103,7 @@ module Youtube
     end
 
     def sync_post_tags! post, desired_tag_ids, current_tag_ids: nil
-      current_tag_ids ||= PostTag.kept.where(post_id: post.id).pluck(:tag_id).to_set
+      current_tag_ids ||= PostTag.where(post_id: post.id).pluck(:tag_id).to_set
       desired_tag_ids = desired_tag_ids.compact.to_set
 
       to_add = desired_tag_ids - current_tag_ids
@@ -117,8 +117,8 @@ module Youtube
         end
       end
 
-      PostTag.where(post_id: post.id, tag_id: to_remove.to_a).kept.find_each do |pt|
-        pt.discard_by!(nil)
+      PostTag.where(post_id: post.id, tag_id: to_remove.to_a).find_each do |pt|
+        pt.destroy!
       end
     end