[ad-hoc] [3](3) Rounding issues in mirror strategy causing offers to not be placed

[nikhilsaraf]

bids are not placed in most situations.

See line below, when dividing by price we may round up to get the normalizedPrimaryUnits and when we eventually multiply again to get back into the quote asset it ends up in a larger number because of this rounding. We want to round down in this case to be conservative, and to take a calculation that has a larger precision output, maybe even consider big.Rat temporarily

normalizedPrimaryUnits = normalizedPrimaryUnits.Divide(*price)

this causes the oversell statement to be triggered, and we don't retry in the mirror strategy yet

• add a test case for checkBalance with the rounding issue using a good volume and price (TDD)
  • name: negative rounding oversell (link this bug in comment)
  • primary quote balance is 646.1
  • backing base balance is 2
  • price is 368
  • zero case
• MultiplyRoundDown + TestMath update
• DivideRoundDown + TestMath update
• use a larger precision for internal calculations and eventually round down in checkBalance

Related to #524