Greenland IBAN parsing rules

Examples

    iex>  %IbanEx.Iban{
    ...>    country_code: "GL",
    ...>    check_digits: "89",
    ...>    bank_code: "6471",
    ...>    branch_code: nil,
    ...>    national_check: nil,
    ...>    account_number: "0001000206"
    ...>  }
    ...>  |> IbanEx.Country.GL.to_string()
    "GL 89 6471 0001000206"