Use transactionId to group parallel reservations, not record ID

..which can be different from reservation to reservation, even if they
are parallel

src/core/utils/useGetReservationGroups.ts

@@ -29,7 +29,7 @@ export type ReservationGroupDetails = Omit<
 function groupReservations(data: ReservationDetailsV2[]) {
   const reservationGroups = groupBy(data, (reservation) => {
     if (reservation.reservationType === "parallel") {
-      return reservation.recordId;
+      return reservation.transactionId;
     }
     return reservation.reservationId;
   });