graph+rpcserver: add InboundFee to ChannelEdgeUpdate

And then use that new field instead of parsing from extra opaque data.

rpcserver.go

@@ -6776,23 +6776,6 @@ func marshalExtraOpaqueData(data []byte) map[uint64][]byte {
 	return records
 }
 
-// extractInboundFeeSafe tries to extract the inbound fee from the given extra
-// opaque data tlv block. If parsing fails, a zero inbound fee is returned. This
-// function is typically used on unvalidated data coming stored in the database.
-// There is not much we can do other than ignoring errors here.
-func extractInboundFeeSafe(data lnwire.ExtraOpaqueData) lnwire.Fee {
-	var inboundFee lnwire.Fee
-
-	_, err := data.ExtractRecords(&inboundFee)
-	if err != nil {
-		// Return zero fee. Do not return the inboundFee variable
-		// because it may be undefined.
-		return lnwire.Fee{}
-	}
-
-	return inboundFee
-}
-
 func marshalDBEdge(edgeInfo *models.ChannelEdgeInfo,
 	c1, c2 *models.ChannelEdgePolicy) *lnrpc.ChannelEdge {
 
@@ -7349,9 +7332,7 @@ func marshallTopologyChange(
 		customRecords := marshalExtraOpaqueData(
 			channelUpdate.ExtraOpaqueData,
 		)
-		inboundFee := extractInboundFeeSafe(
-			channelUpdate.ExtraOpaqueData,
-		)
+		inboundFee := channelUpdate.InboundFee.UnwrapOr(lnwire.Fee{})
 
 		channelUpdates[i] = &lnrpc.ChannelEdgeUpdate{
 			ChanId: channelUpdate.ChanID,