allow to unarchive submissions

app/controllers/submissions_unarchive_controller.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+class SubmissionsUnarchiveController < ApplicationController
+  load_and_authorize_resource :submission
+
+  def create
+    @submission.update!(archived_at: nil)
+
+    redirect_to submission_path(@submission), notice: I18n.t('submission_has_been_unarchived')
+  end
+end