breacharbiter: add chainhash to retributionInfo struct

In this commit we add a chainhash field to the retributionInfo struct
as within the database, channels are now further namespaced by their
chain hash, and all ChannelCloseSummary structs now also carry the
chain hash of their respective chain.

breacharbiter.go

@@ -777,6 +777,7 @@ func (b *breachArbiter) breachObserver(contract *lnwallet.LightningChannel,
 		// BreachClose.
 		closeInfo := &channeldb.ChannelCloseSummary{
 			ChanPoint:      *chanPoint,
+			ChainHash:      breachInfo.ChainHash,
 			ClosingTXID:    breachInfo.BreachTransaction.TxHash(),
 			RemotePub:      &chanInfo.RemoteIdentity,
 			Capacity:       chanInfo.Capacity,
@@ -918,6 +919,7 @@ var _ SpendableOutput = (*breachedOutput)(nil)
 type retributionInfo struct {
 	commitHash chainhash.Hash
 	chanPoint  wire.OutPoint
+	chainHash  chainhash.Hash
 
 	// TODO(conner): remove the following group of fields after decoupling
 	// the breach arbiter from the wallet.
@@ -1007,6 +1009,7 @@ func newRetributionInfo(chanPoint *wire.OutPoint,
 
 	return &retributionInfo{
 		commitHash:      breachInfo.BreachTransaction.TxHash(),
+		chainHash:       chanInfo.ChainHash,
 		chanPoint:       *chanPoint,
 		remoteIdentity:  &chanInfo.RemoteIdentity,
 		capacity:        chanInfo.Capacity,
@@ -1325,6 +1328,10 @@ func (ret *retributionInfo) Encode(w io.Writer) error {
 		return err
 	}
 
+	if _, err := w.Write(ret.chainHash[:]); err != nil {
+		return err
+	}
+
 	if _, err := w.Write(
 		ret.remoteIdentity.SerializeCompressed()); err != nil {
 		return err
@@ -1371,6 +1378,15 @@ func (ret *retributionInfo) Decode(r io.Reader) error {
 		return err
 	}
 
+	if _, err := io.ReadFull(r, scratch[:32]); err != nil {
+		return err
+	}
+	chainHash, err := chainhash.NewHash(scratch[:32])
+	if err != nil {
+		return err
+	}
+	ret.chainHash = *chainHash
+
 	if _, err = io.ReadFull(r, scratch[:33]); err != nil {
 		return err
 	}