@type connectivity() :: :online | :offline | :unknown

@type t() :: %Sumup.ReaderStatus{
  battery_level: float() | nil,
  battery_temperature: integer() | nil,
  connection_type: String.t() | nil,
  firmware_version: String.t() | nil,
  last_activity: DateTime.t() | nil,
  raw: map(),
  state: String.t() | nil,
  status: connectivity()
}