Validate a sort_indep_by key against what add_indep_order() implements
Source: R/sorting_utils.R
validate_sort_indep_by.Rdadd_indep_order() previously fell back to an unsorted seq_len(nrow(data))
for anything it did not recognize, so a typo silently produced unsorted
output with no indication that the argument had been ignored (#600).
Usage
validate_sort_indep_by(sort_by, data, call = rlang::caller_env())