CheckpointContents are the transactions included in an upcoming checkpoint.
They must have already been causally ordered. Since the causal order
algorithm is the same among validators, we expect all honest validators to
come up with the same order for each checkpoint content.
Representation of a Checkpoint’s digest
This is a message validators publish to consensus in order to sign
checkpoint
The Sha256 digest of an EllipticCurveMultisetHash committing to the live
object set.
Same as CheckpointContents, but contains full contents of all Transactions
and TransactionEffects associated with the checkpoint.