Add a possibility not to indicate the schedule reservation on product variants and vice versa

As part of the organization of an event, it is quite possible to offer certain product variants without imposing reservation time slots. This approach simplifies the process, by leaving these variants freely available, without their selection being conditioned by a prior reservation. Concretely, participants can opt for these variants at the time of their arrival, without time constraints or obligation to synchronize with other choices. Thus, we lighten the management of registrations and we avoid complicating the selection for other products or services that require hourly reservations. This flexibility offers not only time savings, but also a smoother experience for participants, while maintaining the possibility of combining these free variants with those subject to reservation if necessary. In summary, making the reservation of certain variants optional helps to simplify the logistics of the event and streamline the journey of the participants, without compromising the general organization.