add: reversed keyword and api forbidden

app/models/reversed_keyword.rb

@@ -0,0 +1,16 @@
+# == Schema Information
+#
+# Table name: reversed_keywords
+#
+#  id          :integer          not null, primary key
+#  identifier  :string(255)
+#  description :text(65535)
+#  closed      :boolean          default("0")
+#  created_at  :datetime         not null
+#  updated_at  :datetime         not null
+#
+
+class ReversedKeyword < ApplicationRecord
+
+  scope :is_reversed, -> (identifier){where(identifier: identifier, closed: false) if identifier.present?}
+end