Add annotate_rb gem and annotate all models

app/models/session.rb

@@ -1,3 +1,22 @@
+# == Schema Information
+#
+# Table name: sessions
+#
+#  id         :integer          not null, primary key
+#  ip_address :string
+#  user_agent :string
+#  created_at :datetime         not null
+#  updated_at :datetime         not null
+#  user_id    :integer          not null
+#
+# Indexes
+#
+#  index_sessions_on_user_id  (user_id)
+#
+# Foreign Keys
+#
+#  user_id  (user_id => users.id)
+#
 class Session < ApplicationRecord
   belongs_to :user
 end