Pakistan IBAN parsing rules

Examples

    iex>  %IbanEx.Iban{
    ...>    country_code: "PK",
    ...>    check_digits: "36",
    ...>    bank_code: "SCBL",
    ...>    branch_code: nil,
    ...>    national_check: nil,
    ...>    account_number: "0000001123456702"
    ...>  }
    ...>  |> IbanEx.Country.PK.to_string()
    "PK 36 SCBL 0000001123456702"