feat: support VDS requested assignment 3 from MMRIVER 02 (#35)

* fix: replciation issue local log and seal corruption

When replicating the remote log file and the remote seal to local disc
the files must be opened in O_TRUNC mode.

The single corner case where this happens required file system based
tests and we only have those in veracity.

Follow on work required if we want those tests to exist in this repo.

AB#10163

* feat: support VDS requested assignment 3 from MMRIVER 02

The presigned receipts will use VDS=3 once the merklesealer takes this
change.

Impact

Receipt verifiers will need accept VDS 3.

Receipt verifiers can confirm the VDS to expect by examining any
replica's latest seal.

Receipt verifiers can safely accept both VDS 2 or VS3 if they know out
of band the receipt came from a forestrie log.

Receipt creators *may* need to accomodate the VDS change, depending on
the depth of validation and sanity checking they perform on pre-signed
receipts before attaching proofs.

This change does not affect:
* replication via veracity.
* checkpoint verification.

---------

Co-authored-by: Robin Bryce <[email protected]>

massifs/rootsigner.go

@@ -20,16 +20,23 @@ type MMRStateVersion int
 
 const (
 	MMRStateVersion0 MMRStateVersion = iota // Implicit initial release version
-	MMRStateVersion1                        // Version 1
+	MMRStateVersion1                        // Version 1 is DRAFT_00 vds =2
+	// Version2 was introduced to indicate support for MMRIVER 02.
+	// In this draft we co-ordinated a requested assignment for the vds and in
+	// doing so ended up with 3 rather than 2.
+	// Note that this change _does not_ impact verification of the checkpoints.
+	// It only impacts the presigned receipts attached in the unprotected headers.
+	MMRStateVersion2 // Version 1 is DRAFT_02 vds =3 (otherwise compatible with v1)
 	// Note: new versions must be monotonicaly assigned.
 
 )
 
 const (
-	MMRStateVersionCurrent  = MMRStateVersion1
+	MMRStateVersionCurrent  = MMRStateVersion2
 	VDSCoseReceiptsTag      = 395
 	VDSCoseReceiptProofsTag = 396
-	VDSMMRiver              = 2
+	VDSMMRiver_DRAFT00      = 2
+	VDSMMRiver              = 3
 	VDSInclusionProof       = -1
 	InclusionProofIndex     = 1
 	InclusionProofProof     = 2