[Fix #1729] Clean mail templates with <code> tags

lib/tasks/2018_03_29_remove_code_tags_from_mail_templates.rake

@@ -0,0 +1,18 @@
+namespace :'2018_03_29_remove_code_tags_from_mail_templates' do
+  task clean: :environment do
+    remove_code_tag_from_body(Mails::ClosedMail)
+    remove_code_tag_from_body(Mails::InitiatedMail)
+    remove_code_tag_from_body(Mails::ReceivedMail)
+    remove_code_tag_from_body(Mails::RefusedMail)
+    remove_code_tag_from_body(Mails::WithoutContinuationMail)
+  end
+
+  def remove_code_tag_from_body(model_class)
+    mails = model_class.where("body LIKE ?", "%<code>%")
+    puts "#{mails.count} #{model_class.name} to clean"
+    mails.each do |m|
+      puts "cleaning #{model_class.name} ##{m.id}"
+      m.update(body: m.body.gsub("<code>", "").gsub("</code>", ""))
+    end
+  end
+end