send emails to the support user on new comments

app/services/ee/notification_service.rb

+module EE
+  module NotificationService
+    # override
+    def send_new_note_notifications(note)
+      super
+      send_service_desk_notification(note)
+    end
+
+    def send_service_desk_notification(note)
+      return true unless Gitlab::EE::ServiceDesk.enabled?
+      return true unless note.noteable_type == 'Issue'
+      issue = note.issuable
+      reply_to = issue.service_desk_reply_to
+      return nil unless issue.service_desk_reply_to.present?
+      return nil unless issue.project.service_desk_enabled?
+
+      return nil unless issue.subscribed?(user, issue.project)
+
+      Notify.service_desk_new_note_email(issue.id, note.id)
+    end
+  end
+end

app/services/notification_service.rb

@@ -6,6 +6,8 @@
 #   NotificationService.new.new_issue(issue, current_user)
 #
 class NotificationService
+  prepend EE::NotificationService
+
   # Always notify user about ssh key added
   # only if ssh key is not deploy key
   #