Upgrade Setup

We will use the UpgradeBeacon pattern to implement three upgradable contract types: Home, Replica, and GovernanceRouter.

Each upgradable contract will have:

Proxy
- the permanent address of the contract that external entities interact with
- holds the storage of the contract
- uses the logic specified by Implementation
- uses delegatecall to forward contract calls from Proxy → UpgradeBeacon → Implementation
UpgradeBeacon
- stores the (mutable) address of the Implementation
- forwards delegatecalls to the Implementation
- accepts new Implementation addresses from its Controller (thereby performing upgrades for all Proxies)
Implementation
- specifies the logic of the contract
- code is the same as a normal, non-upgradable contract implementation (though it should use upgrade-safe storage)

Each of the three UpgradeBeacon contracts will share a the same Controller — the contract with the power to perform upgrades.

The Controller contract will have two roles: controller and saver.

controller
- is a transferrable role that should be performing upgrades in almost every case.
- will be set to the GovernanceRouter Proxy, so that the Governance xApp ultimately controls the upgrades of the entire system. Note that this creates a circular dependency which makes upgrades of the GovernanceRouter Implementation particularly sensitive.
saver
- is a transferrable(?) role that is responsible for recovering the system in a catastrophic failure case. Actions performed by the saver will be subject to a timelock enforced by the Controller contract.
- will be set to a multisig contract where the signatories are a set of known / trusted community members. the signatories for the saver multisig be the same on every chain

Diagrams

TODO

TODO (similar to Home or Replica but extra-sensitive b.c. potential to mess up upgradability function)

TODO