def get_doi_ra(doi)
      prefix = validate_prefix(doi)
      return nil if prefix.blank?

      url = "https://doi.org/ra/#{prefix}"
      result = Maremma.get(url)

      result.body.dig("data", 0, "RA")
    end
def get_doi_ra(doi)
      prefix = validate_prefix(doi)
      return nil if prefix.blank?

      url = "https://doi.org/ra/#{prefix}"
      result = Maremma.get(url)

      result.body.dig("data", 0, "RA")
    end
get DOI registration agency