Add test for sign typed data with bytes

[Gudahtt]

This is a rebase of #28. This is the original description:

Added test that contain bytes for signing typed data.

The test values have been calculated with the following smart contract:

pragma solidity 0.4.24;

contract Test {
    
    function personData()
        public
        pure
        returns (bytes) 
    {
        bytes32 personSchemaHash = keccak256("Person(string name,address wallet)");
        return abi.encode(
            personSchemaHash,
            keccak256('Bob'),
            address(0xbBbBBBBbbBBBbbbBbbBbbbbBBbBbbbbBbBbbBBbB)
        );
    }
    
    function signData()
        public
        pure
        returns (bytes) 
    {
        bytes32 personSchemaHash = keccak256("Person(string name,address wallet)");
        return abi.encode(
            mailSchemaHash(),
            keccak256(
                abi.encode(
                    personSchemaHash,
                    keccak256('Cow'),
                    address(0xCD2a3d9F938E13CD947Ec05AbC7FE734Df8DD826)
                )
            ),
            keccak256(personData()),
            keccak256("Hello, Bob!"),
            keccak256(hex"25192142931f380985072cdd991e37f65cf8253ba7a0e675b54163a1d133b8ca")
        );
    }
    
    function signHash()
        public
        pure
        returns (bytes32) 
    {
        return keccak256(signData());
    }
    
    function sign()
        public
        pure
        returns (bytes32) 
    {
        return keccak256(abi.encodePacked(
            byte(0x19), 
            byte(1), 
            0xf2cee375fa42b42143804025fc449deafd50cc031ca257e0b194a650a912090f, 
            signHash()
        ));
    }
    
    
    function mailSchemaHash() 
        public
        pure
        returns (bytes32) 
    {
        return keccak256("Mail(Person from,Person to,string contents,bytes payload)Person(string name,address wallet)");
    }
}

[adonesky1]

@Gudahtt my solidity knowledge needs some buffing but just a general question does the bytes type ultimately allow any string?

[Gudahtt]

I'm not entirely sure - I don't know much about solidity either. But I just looked this up, and it looks like "bytes" is expected to be an array of byte values, where each byte is a number from 1-32 inclusive. The intended encoding seems ambiguous to me though 🤔. I'll have to look into that.

[Gudahtt]

It looks like we accept any string at the moment. Presumably each character represents some number of bytes. Not 100% sure how that gets interpreted though, i.e. which string encoding.

[rekmarks]

LGTM!