fix: remove signature assoc type from tx response trait

[prestwich]

Motivation

#1328 broke network abstraction by adding a signature assoc type to tx response. Some networks have multiple (or missing like in Optimism) signature types. Adding an assoc type here would require adding a signature abstraction enum on a per-network basis (e.g. optimism would require enum OpSigs { Ecdsa(Signature), Deposit }

In general, not all transactions on a network will have the same signature type, so mandating a specific associated type prevents accurately representing Optimism. The current fn signature(&self) -> Option<Self::Signature> (which handles the OP representation effectively), doesn't accurately model Ethereum in which all txns must have a signature.

Solution

Remove the signature associated type, which is unused within the library

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes

[klkvr]

agreed that Option here is not great

going from TransactionResponse to signature would be trivial once we enforce AsRef<TxEnvelope> in #1460, so this should be fine

cc @emhane wondering if we're already using this in reth?

[prestwich]

cc @emhane wondering if we're already using this in reth?

grep shows it's unused in reth. checked all files that import or reference TransactionResponse

[emhane]

should be fine to get the signature via new reth trait SignedTransaction::Signature. Op needs a specific transaction to remove optimism feature gated code, see paradigmxyz/reth#11573

[mattsse]

makes sense, this was perhaps premature