VM Message Updating

[dutterbutter]

Although areas of the message subsystem are incomplete, the following task describes the required structures and methods mentioned in the specification that can begin to be stubbed or filled out. Most of the methods listed below are considered IMPL_FINISH so refer to existing implementations.

Some message structures have already been started, see messages crate here.

Methods required:

• Verify

Relevant links to existing implementations:

• Lotus Message Type
• Lotus Message Related Methods

[austinabell]

Last time I checked, the big int type we use has all of the functionality needed referenced here, so probably no need to implement most of those. If we were to, it would probably be reopening up changes from #135 but I doubt it will be necessary. One benefit I see now is that we could be able to implement serialize and deserialize on the wrapped type to avoid the annoyance of manual implementations or remote derives when types use the big int.

As for the message methods, sign is already implemented, but I could see the function being updated to take unsigned as a self reference and converting it to a signed message, where now the sign function is just a constructor of SignedMessage.

Verify is the only function here I think that is missing and will be needed (was waiting for spec to be more complete before doing that one)

Edit: Also if the values in a message type need to be changed to be mutable, the code must be updated. Once a message is created it is not able to be mutated currently (as that seemed correct) but there may be a need to change values if parts of the spec I haven't seen require it)