### Inflation formula improvements

- [ ] set `ideal_stake` (perquintill) through governance (`root_track`), instead of using the number of parachain slots to calculate
- [ ] set `max_annual_inflation` (perquintill) through governance (`root_track`)
- [ ] set `min_annual_inflation` (perquintill) through governance (`root_track`)
- [ ] set `falloff` (perquintill) through governance (`root_track`)
- [ ] set `max_staking_rewards` (perquintill) through governance (`root_track`)
- [ ] all values should default to the current ones

### Current implementation:

pub fn era_payout(
	total_staked: Balance,
	total_stakable: Balance,
	max_annual_inflation: Perquintill,
	period_fraction: Perquintill,
	auctioned_slots: u64,
) -> (Balance, Balance) {
	use pallet_staking_reward_fn::compute_inflation;
	use sp_runtime::traits::Saturating;

	let min_annual_inflation = Perquintill::from_rational(25u64, 1000u64);
	let delta_annual_inflation = max_annual_inflation.saturating_sub(min_annual_inflation);

	// 30% reserved for up to 60 slots.
	let auction_proportion = Perquintill::from_rational(auctioned_slots.min(60), 200u64);

	// Therefore the ideal amount at stake (as a percentage of total issuance) is 75% less the
	// amount that we expect to be taken up with auctions.
	let ideal_stake = Perquintill::from_percent(75).saturating_sub(auction_proportion);

	let stake = Perquintill::from_rational(total_staked, total_stakable);
	let falloff = Perquintill::from_percent(5);
	let adjustment = compute_inflation(stake, ideal_stake, falloff);
	let staking_inflation =
		min_annual_inflation.saturating_add(delta_annual_inflation * adjustment);

	let max_payout = period_fraction * max_annual_inflation * total_stakable;
	let staking_payout = (period_fraction * staking_inflation) * total_stakable;
	let rest = max_payout.saturating_sub(staking_payout);

	let other_issuance = total_stakable.saturating_sub(total_staked);
	if total_staked > other_issuance {
		let _cap_rest = Perquintill::from_rational(other_issuance, total_staked) * staking_payout;
		// We don't do anything with this, but if we wanted to, we could introduce a cap on the
		// treasury amount with: `rest = rest.min(cap_rest);`
	}
	(staking_payout, rest)
}