Add generic API endpoint for arbitrary on-chain parsing logic

[Divide-By-0]

Define some sort of API endpoint that can be hit with a smart contract, selector, and arguments, and then automatically determine how the ether-email-auth parsing is defined on chain with the arguments replaced, and send an email to the user, then send it on-chain when they reply. This lets anyone just write smart contracts and use the same relayer to control it. This will be needed for the hackathon.