watchtower/wtclient/session_queue: unify logging

watchtower/wtdb/client_session.go

@@ -1,6 +1,7 @@
 package wtdb
 
 import (
+	"fmt"
 	"io"
 
 	"github.com/btcsuite/btcd/btcec"
@@ -160,6 +161,11 @@ func (b *BackupID) Decode(r io.Reader) error {
 	)
 }
 
+// String returns a human-readable encoding of a BackupID.
+func (b *BackupID) String() string {
+	return fmt.Sprintf("backup(%x, %d)", b.ChanID, b.CommitHeight)
+}
+
 // CommittedUpdate holds a state update sent by a client along with its
 // allocated sequence number and the exact remote commitment the encrypted
 // justice transaction can rectify.