Azerbaijan IBAN parsing rules

Examples

    iex>  %IbanEx.Iban{
    ...>    country_code: "AZ",
    ...>    check_digits: "21",
    ...>    bank_code: "NABZ",
    ...>    branch_code: nil,
    ...>    national_check: nil,
    ...>    account_number: "00000000137010001944"
    ...>  }
    ...>  |> IbanEx.Country.AZ.to_string()
    "AZ 21 NABZ 00000000137010001944"