Add `check_cols()` function to error on missing columns

[peterdesmet]

It is possible to provide any package to write_dwc(). That package might be missing required resources (already covered) or fields that are used in the mapping. For example, the 2014_demer dataset currently deposited on MDA does not have tag_serial_number in animals. The user currently gets a deep dplyr error for this. It might be useful to provide an error earlier.

I suggest a generic check_cols() function (name similar to expand_cols()), called from within create_animal_occurrences() and create_gps_occurrences():

required_cols <- c("animal_id", "tag_serial_number")
check_cols(animals, required_cols)

It would return TRUE if all is fine, but return a nice error if one of the provided columns is not present. See https://github.com/inbo/movepub/blob/7c20e5aabfa2213a6605e35ffd4fed6d6664e4e5/R/check_ref.R#L16-L24 for inspiration on the error message.

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• The function can later be called from create_ano() too.
• The required_cols could be maintained in each function and test or be stored as globals.