Browser based email wallet connector

[saleel]

Allow dApp websites to easily integrate with EmailWallet by installing a JS script.

The JS script will

• inject window.ethereum and listen to calls made to it based on the spec.
• intercept transactions and generate calldata that matches Email Wallet Execute operation.
• Generate a mail to link with subject like `Execute 0x{calldata}.
• Open the mailto link.

The ideal behaviour for a Uniswap UI would be

• User clicks "Use Email Wallet" button
• UI reflects to show connected status
• User enter amounts to swap, and click "Swap" button
• Their email app opens with a new email to the relayer with subject "Execute: 0xababa..."
• Once they send the email, the desired Swap happens.

There is a MVP / WIP in connect-email-wallet branch.

[Divide-By-0]

So what's missing in the browser-connector branch?

[saleel]

Its only a MVP that opens the mailto link for a target+call data. We want a script that others can include in their UI that implements the functionality in generic way - ideally confirming to https://eips.ethereum.org/EIPS/eip-1193

[Divide-By-0]

This can also be done by a chrome extension that injects itself into login flows.

[saleel]

It would be better if users don't have to install any extensions. Dapps can install our JS SDK to interact with user's email wallet.

• In "browser-connector" model we open the mailto link for each transaction the user want to make in the dapp; or we send an email to the user and ask them to reply.
• In "email-oauth" model we do email send/reply only once and then use ephemeral keys.

(both are kind of oauth as in "Sign in with Email Wallet", just differs in the flow/security model)

Anyway, implementation of browser-connector is not complete in this branch. There is a rough MVP, but there is no SDK that others can integrate yet.
We can probably close this issue, and open a new one later based on which of the above approach we are going to take.