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/models/post.rb

@@ -55,11 +55,10 @@ class Post < ApplicationRecord
   belongs_to :uploaded_user, class_name: 'User', optional: true
 
   has_many :post_tags, dependent: :destroy, inverse_of: :post
-  has_many :active_post_tags, -> { kept }, class_name: 'PostTag', inverse_of: :post
-  has_many :post_tags_with_discarded, -> { with_discarded }, class_name: 'PostTag'
-  has_many :tags, through: :active_post_tags
+  has_many :tags, through: :post_tags
   has_many :active_tags, -> { where(tags: { deprecated_at: nil }) },
-           through: :active_post_tags, source: :tag
+           through: :post_tags,
+           source: :tag
 
   has_many :user_post_views, dependent: :delete_all
   has_many :post_similarities, dependent: :delete_all
@@ -123,7 +122,6 @@ class Post < ApplicationRecord
 
   def snapshot_tag_names
     post_tags
-        .kept
         .joins(tag: :tag_name)
         .includes(:sections, tag: :tag_name)
         .order('tag_names.name')
@@ -150,7 +148,6 @@ class Post < ApplicationRecord
 
   def snapshot_tags_json
     post_tags
-        .kept
         .joins(tag: :tag_name)
         .includes(:sections, tag: :tag_name)
         .order('tags.id')