@type metadata_item() :: %{name: String.t(), value: term()}

@type t() :: %Daraja.Express.Callback.Result{
  callback_metadata: [metadata_item()],
  callback_metadata_map: %{optional(String.t()) => term()},
  checkout_request_id: String.t() | nil,
  merchant_request_id: String.t() | nil,
  result_code: integer() | String.t() | nil,
  result_desc: String.t() | nil
}