[Epic] 3.3: Factor out ETH Flow from core services

[fleupold]

Epic label: E:3.3 Factor out ETHFlow
Planned start date: 01.11.2023
Due date: 31.12.2023

Summary

ETH Flow was developed under time pressure before basic protocol features such as pre/post interactions and generalized ERC1271 support had been implemented for the core services.

As a consequence we have create a lot of logic, special code paths and edge cases in the core services repository in order to make ETH Flow work.
With the development of hooks and initiatives like TWAP it has become apparent that ETH Flow should be treated not as a core protocol feature, but instead be part of the periphery and use protocol primitives such as hooks and ERC1271 orders to achieve the same user outcome.

This EPIC captures refactoring the ETH flow logic into a periphery service (similar to or even part of the watch-tower) so that the core services no longer have to special case these orders.

Acceptance Criteria

• Core services are completely agnostic to ETH flow orders.
• Native ETH flow orders are placed using the standard public API
• Users still have the same user experience in the App and explorer

Tasks