The new functionality we have added to the forms is the option to include a confirmation field in the form settings. This way, before booking with you, your customers will have to check the box of the confirmation field and can open the external link you have included.
IMPORTANT: As of October 1, 2023, the "Form settings" field no longer exists in the event options menu. This customization of the events must be done from the flows. It is necessary to create the form flows to customize the information requested from your customers when they make a booking with you.