graph/db+rpcserver: remove inbound fee extraction

For any call-site where we extract inbound fees from a
models.ChannelEdgePolicy object that was deserialised from disk, we can
now just use the new InboundFee field on the object since we know that
it would have been populated at deserialisation time.

Note that for all these call-sites, if a failure previously happened on
decoding of the TLV stream, the error would be ignored and the edge
would just be skipped. This behaviour is now still the same given how
ErrParsingExtraTLVBytes is handled on the DB layer.

graph/db/kv_store.go

@@ -482,16 +482,6 @@ func (c *KVStore) forEachNodeDirectedChannel(tx kvdb.RTx,
 			cachedInPolicy.ToNodeFeatures = toNodeFeatures
 		}
 
-		var inboundFee lnwire.Fee
-		if p1 != nil {
-			// Extract inbound fee. If there is a decoding error,
-			// skip this edge.
-			_, err := p1.ExtraOpaqueData.ExtractRecords(&inboundFee)
-			if err != nil {
-				return nil
-			}
-		}
-
 		directedChannel := &DirectedChannel{
 			ChannelID:    e.ChannelID,
 			IsNode1:      node == e.NodeKey1Bytes,
@@ -499,7 +489,12 @@ func (c *KVStore) forEachNodeDirectedChannel(tx kvdb.RTx,
 			Capacity:     e.Capacity,
 			OutPolicySet: p1 != nil,
 			InPolicy:     cachedInPolicy,
-			InboundFee:   inboundFee,
+		}
+
+		if p1 != nil {
+			p1.InboundFee.WhenSome(func(fee lnwire.Fee) {
+				directedChannel.InboundFee = fee
+			})
 		}
 
 		if node == e.NodeKey2Bytes {

rpcserver.go

@@ -6842,7 +6842,7 @@ func marshalDBRoutingPolicy(
 	disabled := policy.ChannelFlags&lnwire.ChanUpdateDisabled != 0
 
 	customRecords := marshalExtraOpaqueData(policy.ExtraOpaqueData)
-	inboundFee := extractInboundFeeSafe(policy.ExtraOpaqueData)
+	inboundFee := policy.InboundFee.UnwrapOr(lnwire.Fee{})
 
 	return &lnrpc.RoutingPolicy{
 		TimeLockDelta:    uint32(policy.TimeLockDelta),
@@ -7698,14 +7698,9 @@ func (r *rpcServer) FeeReport(ctx context.Context,
 				edgePolicy.FeeProportionalMillionths
 			feeRate := float64(feeRateFixedPoint) / feeBase
 
-			// Decode inbound fee from extra data.
-			var inboundFee lnwire.Fee
-			_, err := edgePolicy.ExtraOpaqueData.ExtractRecords(
-				&inboundFee,
+			inboundFee := edgePolicy.InboundFee.UnwrapOr(
+				lnwire.Fee{},
 			)
-			if err != nil {
-				return err
-			}
 
 			// TODO(roasbeef): also add stats for revenue for each
 			// channel