Web SDK v3: advanced call scheduling

Advanced call scheduling has the following capabilities:

• Day-based time slot selection. End-users can browse available time slots organized by day, with configurable intervals. • Rescheduling. If an end-user reopens the web SDK and has an existing scheduled call, they're prompted to manage that appointment (reschedule or cancel) before starting a new flow. • Cancellation. End-users can cancel a previously scheduled call using the web SDK.