CoW AMM Router: CoW Sender transfers to Vault upfront (No approval)

[joaobrunoah]

Description

The sender (CoW Settlement, or any EOA/contract calling the CoW Router) currently needs to give approval to the router, so the router is able to transfer funds from the sender to the vault. However, this approach is not very flexible, in a way that if the token has any fee on transfer implemented, the router reverts.

In order to simplify this interaction and don't rely on approvals, the sender can transfer the funds directly to the vault, and only inform the router what's the amount that has been transferred (transferHint). This approach is more flexible, the user is able to transfer more tokens in case of a fee on transfer, or any other use case that requires more flexibility.

Type of change

• Bug fix
• New feature
• Breaking change
• Dependency changes
• Code refactor / cleanup
• Optimization: [ ] gas / [ ] bytecode
• Documentation or wording changes
• Other

Checklist:

• The diff is legible and has no extraneous changes
• Complex code has been commented, including external interfaces
• Tests have 100% code coverage
• The base branch is either main, or there's a description of how to merge

[EndymionJkb]

Looks pretty straightforward; just some naming/comment suggestions.