Riskiest Trove can be made to pay compound interest cheaply

[GalloDaSballo]

Impact

Apollon charges simple interest on Trove Accrual

In general Troves can only be accrued by their owners during state-changing operations

    for (uint i = 0; i < _iterations.length; i++) {
      RedeemIteration memory iteration = _iterations[i];
      checkValidRedemptionHint(vars.priceCache, iteration.trove);
      troveManager.applyPendingRewards(iteration.trove, vars.priceCache); /// @audit The Hint may be wrong NOW, the CR may be underwater now
      SingleRedemptionVariables memory troveRedemption = _calculateTroveRedemption( /// TODO: KEY
        vars.priceCache,
        iteration.trove,
        _stableCoinAmount - vars.totalRedeemedStable,
        false // without pending rewards, because they got applied above
      );

      // resulting CR differs from the expected CR, we bail in that case, because all following iterations will consume too much gas by searching for a updated hints
      // allowing 1% deviation, because of time based borrowing interests
      if (troveRedemption.resultingCR > iteration.expectedCR) {
        if ((troveRedemption.resultingCR * DECIMAL_PRECISION) / iteration.expectedCR > 1.01e18) break; /// @audit Risk of overflow
      } else {
        if ((iteration.expectedCR * DECIMAL_PRECISION) / troveRedemption.resultingCR > 1.01e18) break;
      }

However, the riskiest trove can be made to accrue by redeeming a very small amount of debt (e.g. 1 wei)

Mitigation

Either document this risk, or enforce a minimum redemption size

[sambP]