Sign Typed Data v4
signTypedData_v4 currently represents the latest version of the EIP 712 spec, with added support for arrays and with a breaking fix for the way structs are encoded.
This does not mean it is perfect, and does not mean we will not eventually have a
v4, but we do intend to protect this namespace and keep it comaptible going forwards.
Hopefully soon we will also have good examples for parsing method input into structs for verification on-chain (great contribution opportunity!)