Refactor contact mailer

- Send single email with new email in `to` and old email in `bcc` fields
- Remove `Que::Mailer` (#895)
- Add preview
- DRY templates
- Add tests
- Extract translations
- Remove useless specs

app/mailers/contact_mailer.rb

@@ -1,36 +1,12 @@
 class ContactMailer < ApplicationMailer
-  include Que::Mailer
   helper_method :address_processing
 
-  def email_updated(old_email, email, contact_id, should_deliver)
-    @contact   = Contact.find_by(id: contact_id)
+  def email_changed(contact:, old_email:)
+    @contact = contact
     @old_email = old_email
-    unless @contact
-      Rails.logger.info "Cannot send email in #{self.class.name}##{__method__} with contact_id #{contact_id}. It cannot be found"
-      return
-    end
 
-
-    return unless email || @contact
-    return if delivery_off?(@contact, should_deliver)
-
-    begin
-      mail(to: format(email), subject: "#{I18n.t(:contact_email_update_subject)} [#{@contact.code}]")
-    rescue EOFError,
-           IOError,
-           TimeoutError,
-           Errno::ECONNRESET,
-           Errno::ECONNABORTED,
-           Errno::EPIPE,
-           Errno::ETIMEDOUT,
-           Net::SMTPAuthenticationError,
-           Net::SMTPServerBusy,
-           Net::SMTPFatalError,
-           Net::SMTPSyntaxError,
-           Net::SMTPUnknownError,
-           OpenSSL::SSL::SSLError => e
-      logger.info "EMAIL SENDING FAILED: #{email}: #{e}"
-    end
+    subject = default_i18n_subject(contact_code: contact.code)
+    mail(to: contact.email, bcc: old_email, subject: subject)
   end
 
   private
@@ -38,4 +14,4 @@ class ContactMailer < ApplicationMailer
   def address_processing
     Contact.address_processing?
   end
-end
+end