Renames raw POLIS columns to their canonical Snake_Name via the crosswalk,
then applies janitor::clean_names() to everything the crosswalk does not
cover. The result is fully snake_case with the agreed names for special
tokens.
Examples
raw <- data.frame(PoNS_OnSetDate = 1, Admin0Name = "X", DateOnset = 2,
check.names = FALSE)
names(standardise_names(raw))
#> [1] "pons_on_set_date" "adm0" "date_onset"
