invoices: add missing String() cases

invoices/update.go

@@ -128,6 +128,9 @@ func (u ResolutionResult) String() string {
 	case ResultSettled:
 		return "settled"
 
+	case ResultCanceled:
+		return "canceled"
+
 	case ResultInvoiceNotOpen:
 		return "invoice no longer open"
 
@@ -137,6 +140,9 @@ func (u ResolutionResult) String() string {
 	case ResultMppInProgress:
 		return "mpp reception in progress"
 
+	case ResultMppTimeout:
+		return "mpp timeout"
+
 	case ResultAddressMismatch:
 		return "payment address mismatch"
 
@@ -152,6 +158,9 @@ func (u ResolutionResult) String() string {
 	case ResultKeySendError:
 		return "invalid keysend parameters"
 
+	case ResultInvoiceNotFound:
+		return "invoice not found"
+
 	default:
 		return "unknown"
 	}