Add ability to customize serialization

[IanWold]

Summary

Currently, packets are serialized using messagepack, this feature would allow users to customize the serialization to be able to use others (protobuf, memorypack, etc).

What is motivating this feature?

This is a feature requested for the first-class Redis backplane, would be nice to have.

Detailed Description

• Create an interface for the (de)serialization operations
• Implement the messagepack serialization as a member of this interface
• Inject the messagepack serializer using this interface
• Write documentation on implementing and injecting a custom serializer.

Are there any open questions or investigation needed?

Might take some doing to figure how to separate the logic, it doesn't look difficult but wasn't originally intended to be separated.

This is not a requirement for prod, and will not be done until after prod is launched.