This commit introduces a RetributionStore interface, which
establishes the methods used to access persisted information
regarding breached channels. A RetributionStore is used to
persist retributionInfo regarding all channels for which
the wallet has signaled a breach.
The current design could be improved by moving certain
functionality, e.g. closing channels and htlc links, such
that they are handled by upstream by their respective
subsystems. This was investigated, but deemed preferable to
postpone to a later update to prevent the current
implementation from sprawling amongst too many packages.
The test suite creates a mockRetributionStore and ensures that
it exhibits the same behavior as the retribution store backed
by a channeldb.DB.
This commit adds a breached contract retribution storage layer using
boltdb to the breach arbiter. The breach arbiter now stores retribution
state on disk between detecting a contract breach, broadcasting a
justice transaction that sweeps the channel, and finally witnessing the
justice transaction confirm on the blockchain. It is critical that such
state is persisted on disk, so that if our node restarts at any point
during the retribution procedure, we can recover and continue from the
persisted state.
