Add: #600 NGルール (#602)

* Wip

* Wip

* Wip: History

* Wip: テストコード作成

* Fix test

* Wip

* Wip

* Wip

* Fix test

* Wip

* Wip

* Wip

* Wip

* なんとか完成、これから動作確認

* spell miss

* Change ng rule timings

* Fix test

* Wip

* Fix test

* Wip

* Fix form

* 表示まわりの改善

app/controllers/admin/ng_rule_histories_controller.rb

@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+module Admin
+  class NgRuleHistoriesController < BaseController
+    before_action :set_ng_rule
+    before_action :set_histories
+
+    PER_PAGE = 20
+
+    def show
+      authorize :ng_words, :show?
+    end
+
+    private
+
+    def set_ng_rule
+      @ng_rule = ::NgRule.find(params[:id])
+    end
+
+    def set_histories
+      @histories = NgRuleHistory.where(ng_rule_id: params[:id]).order(id: :desc).page(params[:page]).per(PER_PAGE)
+    end
+  end
+end