lnrpc: add field denoting if channel peer is online in ListChannels

This commit adds a new field to the ListChannels RPC command which
indicates if the peer is currently online or not. This is useful as
UI’s will be able to use this information to communicate the
availability of each channel to an end user.

rpcserver.go

@@ -813,8 +813,8 @@ func (r *rpcServer) ListChannels(ctx context.Context,
 			continue
 		}
 
-		nodePub := dbChannel.IdentityPub.SerializeCompressed()
-		nodeID := hex.EncodeToString(nodePub)
+		nodePub := dbChannel.IdentityPub
+		nodeID := hex.EncodeToString(nodePub.SerializeCompressed())
 		chanPoint := dbChannel.ChanID
 
 		// With the channel point known, retrieve the network channel
@@ -822,7 +822,13 @@ func (r *rpcServer) ListChannels(ctx context.Context,
 		var chanID uint64
 		chanID, _ = graph.ChannelID(chanPoint)
 
+		var peerOnline bool
+		if _, err := r.server.findPeer(nodePub); err == nil {
+			peerOnline = true
+		}
+
 		channel := &lnrpc.ActiveChannel{
+			Active:                peerOnline,
 			RemotePubkey:          nodeID,
 			ChannelPoint:          chanPoint.String(),
 			ChanId:                chanID,