For bills:
    * using frequency and known bills fill in missing gaps
      -- need to add to DB whether the bill was added manually or auto-flled in (so if we want, we can re-calc. based on growth calc change as we add more real bills over time?)
    * need to work out 'first bill' and 'last bill' to auto-fill missing bills based on
      -- all missing bills follow varying growth models & its by choice -- therefore I need this in DB
         - ANN: flat, min, avg, max, manual
         - QTR: flat, qtrly: min/avg/max/manual, annual: min/avg/max/manual
         - MON: flat, monthly: min/avg/max/manual, annual: min/avg/max/manual
      -- use this logic to add missing bills (date):
           -- ANN: missing annual bill, find date based on MM-DD and add new year - given we start with first_bill anyway, will only be used for future bill predictions
           -- QTR: missing quarterly bill, find date based on MM-DD and ??? - can have missing bilsl in first year
           -- MON: missing monthly bills, find date based on DD and put in each missing month 
      -- use this logic to add missing bills (amount):
           -- ANN: future only, so add ann_growth (based on drop-down) for each future year
           -- QTR: add growth (based on drop-down) for each future year
           -- MON: add growth (based on drop-down) for each future year 
    * once auto-filled bills exist:
        - calc growth [DONE]
          -- WARNING: could be chicken/egg here, if not enough bills to calc growth - maybe only offer flat/manual until there are enough??
        - project out to I am 60
            - probably need to allow a toggle to: allow show manual, show auto-filled past, show auto-filled future, show all
        - remove bills from Living_Expenses (carefully - but by hand)
        - fold future bills into calc so they are taken out in a more time and growth appropriate way
        - inflation can then be put to a more realistic quarterly figure

MUCH LONGER/HARDER:
    potentially for each bill_type, there are unique extras - e.g. THIS feels too hard:
        water has 2 fixed charges (water & sewerage) and then a consumption charge (per ML)
        elec has 1 fixe charge (daily) and then consumption (per kwh) BUT, also daily solar rate
        gas has fixed charge and consumption
        internet, kayo is monthly fixed (but can go up sometimes)
        eweka is annual fixed
        phone is messier again.