feat: Add contract astroport-pair-xyk-sale-tax

[apollo-sturdy]

This contract is a copy of the standard XYK pair but adds a configurable tax on swaps.

After launching the APOLLO token, Apollo DAO will be submitting a proposal to migrate standard xyk pair to this contract. If the proposal passes, perhaps it makes sense to merge it into the main astroport-core repo.

[epanchee]

Hi @apollo-sturdy

Isn't this recently added feature does the same thing?

astroport-core/contracts/pair/src/contract.rs

Lines 695 to 718 in 6c753c4

	// If this pool is configured to share fees, calculate the amount to send
	// to the receiver and add the transfer message
	// The calculation works as follows: We take the share percentage first,
	// and the remainder is then split between LPs and maker
	let mut fees_commission_amount = commission_amount;
	let mut fee_share_amount = Uint128::zero();
	if let Some(fee_share) = config.fee_share.clone() {
	// Calculate the fee share amount from the full commission amount
	let share_fee_rate = Decimal::from_ratio(fee_share.bps, 10000u16);
	fee_share_amount = fees_commission_amount * share_fee_rate;
	if !fee_share_amount.is_zero() {
	// Subtract the fee share amount from the commission
	fees_commission_amount = fees_commission_amount.saturating_sub(fee_share_amount);
	// Build send message for the shared amount
	let fee_share_msg = Asset {
	info: ask_pool.info.clone(),
	amount: fee_share_amount,
	}
	.into_msg(fee_share.recipient)?;
	messages.push(fee_share_msg);
	}
	}

[apollo-sturdy]

Hi @apollo-sturdy

Isn't this recently added feature does the same thing?

Thanks for mentioning this, I wasn't aware of this change. However, this doesn't seem to allow us to accomplish what we want. There are a few differences:

• It charges the fee share / tax on the return asset rather than the offer asset.
• It charges the fee rate on top of the commission amount which is set the same for all pairs of the same type, which means we at most would be able to take 100% of the total_fee_rate.

[donovansolms]

Looks good - I have nothing to add.

I hope that tax_config_admin would be some governance address and not a multisig that would allow silent rugging of everyone that swaps via this pool. If it is, I'd much rather have stricter limits on what the tax can be set to.

[epanchee]

LGTM