channeldb: new custom blob nested TLV

In this commit, for each channel, we'll now start to store an optional custom blob. This can be used to store extra information for custom channels in an opauqe manner.

channeldb/channel_test.go

@@ -351,6 +351,7 @@ func createTestChannelState(t *testing.T, cdb *ChannelStateDB) *OpenChannel {
 			FeePerKw:      btcutil.Amount(5000),
 			CommitTx:      channels.TestFundingTx,
 			CommitSig:     bytes.Repeat([]byte{1}, 71),
+			CustomBlob:    fn.Some([]byte{1, 2, 3}),
 		},
 		RemoteCommitment: ChannelCommitment{
 			CommitHeight:  0,
@@ -360,6 +361,7 @@ func createTestChannelState(t *testing.T, cdb *ChannelStateDB) *OpenChannel {
 			FeePerKw:      btcutil.Amount(5000),
 			CommitTx:      channels.TestFundingTx,
 			CommitSig:     bytes.Repeat([]byte{1}, 71),
+			CustomBlob:    fn.Some([]byte{4, 5, 6}),
 		},
 		NumConfsRequired:        4,
 		RemoteCurrentRevocation: privKey.PubKey(),
@@ -374,6 +376,7 @@ func createTestChannelState(t *testing.T, cdb *ChannelStateDB) *OpenChannel {
 		InitialRemoteBalance:    lnwire.MilliSatoshi(3000),
 		Memo:                    []byte("test"),
 		TapscriptRoot:           fn.Some(tapscriptRoot),
+		CustomBlob:              fn.Some([]byte{1, 2, 3}),
 	}
 }
 
@@ -663,6 +666,7 @@ func TestChannelStateTransition(t *testing.T) {
 		CommitTx:        newTx,
 		CommitSig:       newSig,
 		Htlcs:           htlcs,
+		CustomBlob:      fn.Some([]byte{4, 5, 6}),
 	}
 
 	// First update the local node's broadcastable state and also add a
@@ -700,9 +704,14 @@ func TestChannelStateTransition(t *testing.T) {
 	// have been updated.
 	updatedChannel, err := cdb.FetchOpenChannels(channel.IdentityPub)
 	require.NoError(t, err, "unable to fetch updated channel")
-	assertCommitmentEqual(t, &commitment, &updatedChannel[0].LocalCommitment)
+
+	assertCommitmentEqual(
+		t, &commitment, &updatedChannel[0].LocalCommitment,
+	)
+
 	numDiskUpdates, err := updatedChannel[0].CommitmentHeight()
 	require.NoError(t, err, "unable to read commitment height from disk")
+
 	if numDiskUpdates != uint64(commitment.CommitHeight) {
 		t.Fatalf("num disk updates doesn't match: %v vs %v",
 			numDiskUpdates, commitment.CommitHeight)