Defensive: stake if there's a bad assertion.

Make nodes: continually create new nodes, challenging bad assertions.

Resolve nodes: stay staked on the latest node and resolve any unconfirmed nodes, challenging bad assertions.

Watchtower: don't do anything on L1, but log if there's a bad assertion.

ChallengeCreator defines a struct which can initiate a challenge on an assertion hash by creating a level zero, block challenge edge onchain.

ChallengeManager defines an offchain, challenge manager, which will be an active participant in interacting with the on-chain contracts.

ChallengeReader defines a struct which can read the challenge of a challenge manager.