This method posts an XML document containing bookings and invoiced items. The username and password fields must be included in the post. The account APIKEY can be used as the password.
The action parameter of each booking must be either new, delete or modify.
The XML format for the bookings is a bookings element containing booking elements in the same format as returned by the getBookings method.
Only the modified fields of a booking need to be posted when modifying a booking. Booking fields not in the posted XML will not be modified.