- Invoice is generated 15 days before next period and a RR is created
   - 15 later a stop warning is sent (or when invoice expires)
   - 7 days later all instances are stopped if RR still open
    - 5 days after the user is informed his instances will be removed if payment is not done
    - 10 days after ALL his instances will be removed (for safety, as instances can be scaled faster if needed)

So, we assume:

   User is informed 22 days in advance before his instances stop to work, and if nothing is done 15 after (or 37 days after the first request to pay), we just remove all.