The auctioneer will now provide a height hint along with every proposed
batch it sends to traders. This height hint is then used by each trader
to base off their absolute lease expiration height, such that they can
agree on the same value and avoid any divergences due to block
propagation discrepancies between them.
Previously, if the connection between the trader and auctioneer was torn
down before the trader received a batch's finalize message, then the
trader would lose all context about the batch they participated in.
Committing the batch before providing our signatures to the auctioneer
ensures that this cannot happen. Follow-up work will allow the trader to
obtain the latest information regarding a pending batch upon
reconnections.
This commits serves as preparatory work for committing a pending batch
before providing signatures to the auctioneer. This is achieved by first
storing the batch as pending upon receiving a new batch and marking it
as complete upon receiving a finalize message.
