multi: use key locator for lnwallet.MessageSigner

To simplify the message signing API even further, we refactor the
lnwallet.MessageSigner interface to use a key locator instead of the
public key to identify which key should be signed with.

netann/chan_status_manager.go

@@ -8,6 +8,7 @@ import (
 	"github.com/btcsuite/btcd/btcec"
 	"github.com/btcsuite/btcd/wire"
 	"github.com/lightningnetwork/lnd/channeldb"
+	"github.com/lightningnetwork/lnd/keychain"
 	"github.com/lightningnetwork/lnd/lnwallet"
 	"github.com/lightningnetwork/lnd/lnwire"
 )
@@ -43,6 +44,10 @@ type ChanStatusConfig struct {
 	// OurPubKey is the public key identifying this node on the network.
 	OurPubKey *btcec.PublicKey
 
+	// OurKeyLoc is the locator for the public key identifying this node on
+	// the network.
+	OurKeyLoc keychain.KeyLocator
+
 	// MessageSigner signs messages that validate under OurPubKey.
 	MessageSigner lnwallet.MessageSigner
 
@@ -621,7 +626,7 @@ func (m *ChanStatusManager) signAndSendNextUpdate(outpoint wire.OutPoint,
 	}
 
 	err = SignChannelUpdate(
-		m.cfg.MessageSigner, m.cfg.OurPubKey, chanUpdate,
+		m.cfg.MessageSigner, m.cfg.OurKeyLoc, chanUpdate,
 		ChanUpdSetDisable(disabled), ChanUpdSetTimestamp,
 	)
 	if err != nil {