routing: add htlcAmt to PaymentBandwidth method of TlvTrafficShaper

This commit was added to the 0-19-staging branch recently and therefore
didn't make it into a previous part yet. So it's unrelated to the
changes in this part but is required for the whole custom channel saga.

routing/bandwidth.go

@@ -47,7 +47,8 @@ type TlvTrafficShaper interface {
 	// is a custom channel that should be handled by the traffic shaper, the
 	// HandleTraffic method should be called first.
 	PaymentBandwidth(htlcBlob, commitmentBlob fn.Option[tlv.Blob],
-		linkBandwidth lnwire.MilliSatoshi) (lnwire.MilliSatoshi, error)
+		linkBandwidth,
+		htlcAmt lnwire.MilliSatoshi) (lnwire.MilliSatoshi, error)
 }
 
 // AuxHtlcModifier is an interface that allows the sender to modify the outgoing
@@ -191,6 +192,7 @@ func (b *bandwidthManager) getBandwidth(cid lnwire.ShortChannelID,
 			commitmentBlob := link.CommitmentCustomBlob()
 			auxBandwidth, err := ts.PaymentBandwidth(
 				b.firstHopBlob, commitmentBlob, linkBandwidth,
+				amount,
 			)
 			if err != nil {
 				return bandwidthErr(fmt.Errorf("failed to get "+

routing/bandwidth_test.go

@@ -148,7 +148,7 @@ func (*mockTrafficShaper) ShouldHandleTraffic(_ lnwire.ShortChannelID,
 // is a custom channel that should be handled by the traffic shaper, the
 // HandleTraffic method should be called first.
 func (*mockTrafficShaper) PaymentBandwidth(_, _ fn.Option[tlv.Blob],
-	linkBandwidth lnwire.MilliSatoshi) (lnwire.MilliSatoshi, error) {
+	linkBandwidth, _ lnwire.MilliSatoshi) (lnwire.MilliSatoshi, error) {
 
 	return linkBandwidth, nil
 }