* How to handle billing in general
** Orders
   - Orders are the heart of uncloud billing
   - Have a starting date
   - Have an ending date
*** Statuses
    - CREATING/PREPARING
    - INACTIVE (?)
    - TO_BILL / NOT_TO_BILL
*** Updating status of orders
    - If has succeeding order and billing date is last month -> set inactive
** Bills
   - Are always for a month
   - Can be preliminary
*** Which orders to include
    - Not the cancelled ones / not active ones
    -
** Flows / Approach
*** Finding all orders for a bill
    - Get all orders, state != NOT_TO_BILL; for each order do:
      - is it a one time order?
        - has it a bill assigned?
          - yes: set to NOT_TO_BILL
          - no:
            - get_or_create_bill_for_this_month
            - assign bill to this order
            - set to NOT_TO_BILL

    - First of month
    - Last of month