APIs designed to help avoid app link issues with WalletConnect on iOS

[markdalgleish]

This is related to an earlier discussion about populateTransaction (#3151) but I figured this is important enough to have its own discussion.

For some background on the app link issues on iOS, I recently added a new section to the WalletConnect docs site that explains what's happening and provides some guidance on how to avoid it: https://docs.walletconnect.com/mobile-linking#ios-app-link-constraints

As you can see in the Ethers v5 section, there's quite a few gotchas that require some careful workarounds. It feels like there's definitely an opportunity here to provide first-class APIs that would help WalletConnect consumers, allowing them to prepare transactions up-front. There could also potentially be an API for validating that a transaction has already been prepared so that consumers can be sure that any preceding async work has already been done.

You'd obviously have a much better idea on how to integrate this than I would, but I was thinking that there could maybe be an async prepareTransaction method (which would then also be used internally by sendTransaction), as well as a validatePreparedTransaction/isTransactionPrepared util.

The part I'm less sure about is how best to manage the separation between sendTransaction and sendUncheckedTransaction. It's a bit of a footgun for WalletConnect users right now since they need to know to reach for sendUncheckedTransaction instead to avoid any async work. It'd be great if they could somehow be better guided towards the right behaviour. As an example, wagmi is looking to move to unchecked transactions being the default so it's not an issue anymore.

Really interested to hear your thoughts on this 🙏