Guatemala IBAN parsing rules

Examples

    iex>  %IbanEx.Iban{
    ...>    country_code: "GT",
    ...>    check_digits: "82",
    ...>    bank_code: "TRAJ",
    ...>    branch_code: nil,
    ...>    national_check: nil,
    ...>    account_number: "01020000001210029690"
    ...>  }
    ...>  |> IbanEx.Country.GT.to_string()
    "GT 82 TRAJ 01020000001210029690"