feat: Remove uniform clearing prices

[fhenneke]

Problem

With the new mechanism described in CIP-67, uniform clearing prices are removed from the mechanism. But these clearing prices are currently still required on APIs and they are post-processed with derived values stored in the data base (e.g. executed fee amounts).

Suggested solution

Uniform clearing should be removed from the code base.

Additional context

Uniform clearing prices do appear in a few places and it is not obvious how easy it is to remove them.

• They appear in the autopilot<>driver API. Removing them would be a breaking change but should be easy to handle.
• They appear in the driver<>solvre API. Removing them would be a breaking change and a bit more difficult to handle.
• Fee amounts are currently used in the solver accounting.
• There is at least one external dependence in the form of the front end using derived fee amounts to show to users.
• They might appear in other places as well. Generally, though, it should be safe to work with executed amounts instead of clearing prices for

Acceptance criteria

• Uniform clearing should be removed from the autopilot.
• Uniform clearing prices should ideally also be removed from the reference driver. But that has lower priority.

[github-actions]

This issue has been marked as stale because it has been inactive a while. Please update this issue or it will be automatically closed.

[github-actions]

This issue has been marked as stale because it has been inactive a while. Please update this issue or it will be automatically closed.

[fafk]

One does not simply remove the remove the clearing prices from our services. Currently they are needed to calculate fee & surplus in the autopilot: https://github.com/cowprotocol/services/blob/main/crates/autopilot/src/domain/settlement/trade/math.rs#L201.

If we can change the logic here we can unblock the rest.

[MartinquaXD]

If we can change the logic here we can unblock the rest.

From my understanding those are 2 separate points. The thing you linked is about having to encode 2 prices for every trade (price without fees/uniform clearing price, price with fees) in order to compute exactly how much fees a solver captured for a trade.
What I believe this issue is about is to remove the requirement that there can only be 1 price without fees per token in the solution. So we'd probably still have to encode multiple prices for a token it the settlement calldata but it should be possible to have different prices before fees for the same token in different trades.

[jmg-duarte]

If I understand correctly, the settlement contract already allows this:

    /// @param tokens An array of ERC20 tokens to be traded in the settlement.
    /// Trades encode tokens as indices into this array.
    /// @param clearingPrices An array of clearing prices where the `i`-th price
    /// is for the `i`-th token in the [`tokens`] array.
    /// @param trades Trades for signed orders.

— https://github.com/cowprotocol/contracts/blob/c94c595a791681cf8ba7495117dcde397b932885/src/contracts/GPv2Settlement.sol#L113-L117

So it should should be a matter of replacing the HashMap<TokenAddress, Price> with a Vec and pull the thread from there (?)