client_id() :: String.t() | nil

t() :: %ExFtx.OrderPayload{
  client_id: client_id(),
  ioc: boolean(),
  market: ExFtx.Market.name(),
  post_only: boolean(),
  price: number(),
  reduce_only: boolean(),
  side: String.t(),
  size: number(),
  type: String.t()
}