channeldb: migration to flatten the htlc attempts bucket

channeldb/db.go

@@ -17,6 +17,7 @@ import (
 	"github.com/lightningnetwork/lnd/channeldb/migration16"
 	"github.com/lightningnetwork/lnd/channeldb/migration20"
 	"github.com/lightningnetwork/lnd/channeldb/migration21"
+	"github.com/lightningnetwork/lnd/channeldb/migration23"
 	"github.com/lightningnetwork/lnd/channeldb/migration_01_to_11"
 	"github.com/lightningnetwork/lnd/clock"
 	"github.com/lightningnetwork/lnd/kvdb"
@@ -193,6 +194,10 @@ var (
 			number:    22,
 			migration: mig.CreateTLB(setIDIndexBucket),
 		},
+		{
+			number:    23,
+			migration: migration23.MigrateHtlcAttempts,
+		},
 	}
 
 	// Big endian is the preferred byte order, due to cursor scans over