lnrpc+rpcserver: encode custom records as custom channel data

With this commit we encode the custom records as a TLV stream into the
custom channel data field of the invoice HTLC.
This allows the custom data parser to parse those records and replace it
with human-readable JSON on the RPC interface.

subrpcserver_config.go

@@ -11,6 +11,7 @@ import (
 	"github.com/lightningnetwork/lnd/autopilot"
 	"github.com/lightningnetwork/lnd/chainreg"
 	"github.com/lightningnetwork/lnd/channeldb"
+	"github.com/lightningnetwork/lnd/fn"
 	"github.com/lightningnetwork/lnd/htlcswitch"
 	"github.com/lightningnetwork/lnd/invoices"
 	"github.com/lightningnetwork/lnd/lncfg"
@@ -32,6 +33,7 @@ import (
 	"github.com/lightningnetwork/lnd/sweep"
 	"github.com/lightningnetwork/lnd/watchtower"
 	"github.com/lightningnetwork/lnd/watchtower/wtclient"
+	"google.golang.org/protobuf/proto"
 )
 
 // subRPCServerConfigs is special sub-config in the main configuration that
@@ -123,6 +125,7 @@ func (s *subRPCServerConfigs) PopulateDependencies(cfg *Config,
 		modifiers ...netann.NodeAnnModifier) error,
 	parseAddr func(addr string) (net.Addr, error),
 	rpcLogger btclog.Logger, aliasMgr *aliasmgr.Manager,
+	auxDataParser fn.Option[AuxDataParser],
 	invoiceHtlcModifier *invoices.HtlcModificationInterceptor) error {
 
 	// First, we'll use reflect to obtain a version of the config struct
@@ -274,6 +277,20 @@ func (s *subRPCServerConfigs) PopulateDependencies(cfg *Config,
 				reflect.ValueOf(aliasMgr.GetPeerAlias),
 			)
 
+			parseAuxData := func(m proto.Message) error {
+				return fn.MapOptionZ(
+					auxDataParser,
+					func(p AuxDataParser) error {
+						return p.InlineParseCustomData(
+							m,
+						)
+					},
+				)
+			}
+			subCfgValue.FieldByName("ParseAuxData").Set(
+				reflect.ValueOf(parseAuxData),
+			)
+
 		case *neutrinorpc.Config:
 			subCfgValue := extractReflectValue(subCfg)