This end point completes a new booking. Only appointments in the "IN" initial status can be booked.
by saving all the relevant details of the booking.
A valid appointment id is required. Use the appointmentId returned from POST /consumer/v1/appointments.
To update appointment custom field values, use the GET /consumer/v1/appointments/customfields information.
to understand your definitions of custom fields and what key and values to update.
See more information at Appointments Overview and
Custom Booking Fields