Sets up the list of alternative availabilities. If alternative availability is an integer equal to 1, i.e. always available, then repeats it equal to the number of rows in the (padded) data, if not includes the actual availability vector.
prepare_alt_avail(alt_avail, db)A list of alternative availabilites supplied by the user
A data.frame() or tibble() containing the data
A list of alternative availabilities