Denmark IBAN parsing rules

Examples

    iex>  %IbanEx.Iban{
    ...>    country_code: "DK",
    ...>    check_digits: "50",
    ...>    bank_code: "0040",
    ...>    branch_code: nil,
    ...>    national_check: nil,
    ...>    account_number: "0440116243"
    ...>  }
    ...>  |> IbanEx.Country.DK.to_string()
    "DK 50 0040 0440116243"