Increase iBTC target APR 5%->10%. Increase Interlay fee 10%->15%

There are two overall objectives of this proposal:

1. Increase Interlay protocol revenue from the now heavily used iBTC money market
2. Decrease the slope of the iBTC money market curve under high utilization to reduce the APY impact from deposits and withdrawals of collateral (or repayment of loans)

There has been over $1M of iBTC lent to the Interlay money markets for a while. Since Hydra's Omnipool liquidity campaign kicked off in June there has been high demand for Interlay money market iBTC to deposit and farm in the Omnipool (currently about 30% APR). The money market APR is now consistently between 5-30% demonstrating a higher market tolerance for higher borrowing APR. Therefore this proposal will increase the jumpRate or APR at optimal utilization so that the borrowing rate should bounce around 10% instead of 5%. This will increase or optimize Interlay protocol revenue.

Meanwhile there isn't enough iBTC capacity so iBTC is selling for a premium. Therefore with this asymmetric demand for iBTC the Interlay protocol can increase revenue from iBTC. Specifically, the reserveFactor for each Interlay money market depends what portion of the borrower APY goes to the Interlay treasury. For all markets this is currently 10%. This proposal will increase it to 15%.

There are reports of a user quickly withdrawing ~1.0 iBTC and redepositing it so that the money market calculates the APR based on a higher utilization and therefore higher borrowing APR which is delayed in displaying on the Interlay website UI. The best approach would be to institute a fee on withdrawals such as Hydra Omnipool dynamic fee of 0.01%-1%. However, while new feature development is delayed we can alter the iBTC borrowing APR curve so that at high utilization the curve is shallower and therefore adding/removing BTC has less impact on the APR. Currently for every 1% utilization increase (beyond 90%) the APR will increase by 4.5%. (50% - 5% / 100% - 90%). This proposal decreases that slope to 2% APR change for every 1% utilization change by decreasing the target utilization 90% -> 85% and decreasing the max APR slightly 50%->40%. So (40% - 10% / 100% - 85%) = 2%. Although not a perfect solution it should cause website APR to be more accurate or will force the manipulator to make larger deposits and withdrawals.

This proposal compensates me for 3 hours of research and discussion, testing with Chopsticks and creating the proposal.
3hrs x$100/hr = $300 = 18633 INTR at $0.01610/INTR

-- spazcoin