Poland IBAN parsing rules

Examples

    iex>  %IbanEx.Iban{
    ...>    country_code: "PL",
    ...>    check_digits: "61",
    ...>    bank_code: "109",
    ...>    branch_code: "0101",
    ...>    national_check: "4",
    ...>    account_number: "0000071219812874"
    ...>  }
    ...>  |> IbanEx.Country.PL.to_string()
    "PL 61 109 0101 4 0000071219812874"