Splitting an ecopart_obj

At times it might be worthwhile to split an ecopart_obj into multiple. For example, you might want to split casts based on the time of day, station, seasons, etc. split_ecopart_obj() will return a list with each item being an ecopart_obj based on the split. Users must provide an ecopart_obj and a split_by argument. For example:

library(EcotaxaTools)
split_objs <- ecopart_example |>
    split_ecopart_obj(split_by = 'stationid')
# this will produce 3 ecopart_objs
names(split_objs)

[1] "gf" "xx" "hs"