include order log in warning mails for jobs with order="yes"

Desired Behavior

• If an error/warning occurs in an order job a mail is sent containing the task log of the task in which the error occured. Sometimes the task has already processed hundreds of orders which can result in a very big log. Most of this log is unimportant, because the success of previous orders may have nothing to do with the error of the latest order.
• In many cases it's more interesting to see what happened to the order in previous job chain nodes as preconditions set here might have caused the error.
• This is just a rough idea for a future improvement. Implementing will raise questions such as:
  • When should the order log be sent? At every job chain node which causes an error or only after exiting the job chain?
  • What about setback()?
  • If something in spooler_init() caused an error in spooler_process() we won't see it in the order log
  • If an error results in stopping the job, then it is probably more important to send the task log

Maintainer Notes

• This feature will not be implemented to the JobScheduler Engine.
• Instead, this feature will be added as a requirement for a new mail interface plugin that will be provided with a future release.