Reward Vault: Type Safe Checkpointing POC

This Repo contains a proof of concept for a pattern that leverages Solidity's type system to enforce checkpointing before calling mutating functions. This is accomplished by creating "stale" types that wrap the state of the app that expose a getUpdated function. The "stale" versions of the state does not expose any mutating functions. In order for a programmer to mutate the state of the app they must call getUpdated before hand.