Add basic deadline to sections index

app/models/extension.rb

@@ -0,0 +1,21 @@
+# == Schema Information
+#
+# Table name: extensions
+#
+#  id         :integer          not null, primary key
+#  confirmed  :boolean
+#  reason     :text
+#  created_at :datetime         not null
+#  updated_at :datetime         not null
+#
+class Extension < ApplicationRecord
+  def affect_deadline(deadline)
+    return deadline unless confirmed
+
+    deadline + 6.weeks
+  end
+
+  def confirm!
+    update!(confirmed: true)
+  end
+end