/// Compound current borrow rate over elapsed slots
current_borrow_rate: Rate,
let slot_interest_rate = current_borrow_rate.try_div(SLOTS_PER_YEAR)?;
let compounded_interest_rate = Rate::one()
.try_add(slot_interest_rate)?
.try_pow(slots_elapsed)?;
self.cumulative_borrow_rate_wads = self
.cumulative_borrow_rate_wads
.try_mul(compounded_interest_rate)?;
self.borrowed_amount_wads = self
.try_mul(compounded_interest_rate)?;