Upgrabeable Contracts

## Mike's notes

1. Immutability vs Upgradeability - tradeoffs
2. Risks of Upgrading
   • Storage slot contamination
   • Bricking of state / notes
   • Upgades are not immediate
     • They're necessarily delayed.
     • Don't rely on them to beat an attacker in a race.
3. Upgrade
   • Give details of the upgrade function in the ContractInstancePublisher