#890: Add ECDSA.toEthSignedMessageHash(bytes) for abritrary length message hashing

[td-bn]

Fixes #890
Issue link

The PR adds a function toEthSignedMessageHash(bytes) to the ECDSA contract, that works for any length of a bytes array.

PR Checklist

• Tests
• Documentation
• Changelog entry

[Amxx]

Hello @td-bn , and thank you for this PR!

Do you think it would be possible to add a test with a message that is not 32 bytes long?

[td-bn]

@Amxx, I've added said test. Please take a look.

[frangio]

Please add a test in the section that says using web3.eth.sign, so we can confirm that this function is doing the same that eth_sign is doing under the hood.

Also, the function name of the new function should be toEthSignedMessageHash, not toEthSignedMessage. The "hash" part of the name refers to the output, not to the argument. We want to overload the current function so that it also supports bytes arguments.

[frangio]

Thanks @td-bn! I made two small changes in the tests. Note that I replaced the longer string with a short one, because it's easier to tell that it doesn't happen to have length 32.