[Trader bot] Add approach1 to do simplistic trading

[idiom-bytes]

Status quo

The trader bot is implemented in predictoor/trader/trader_agent.py.

It has a do_trade() function.

• It inputs two things:
  • the Feed object. Eg Binance ETH/USDT 5min
  • and the prediction: (amount staked up, amt staked down)
• With those inputs, it trades according to its implemented strategy

Here's what the baseline do_trade() currently is:

 async def do_trade(feed: Feed, prediction: Tuple[float, float]):
    """
    @description
        This function is called each time there's a new prediction available.
        By default, it prints the signal.
        The user should implement their trading algorithm here.
    @params
        feed : Feed
            An instance of the Feed object.

        prediction : Tuple[float, float]
            A tuple containing two float values, the unit is ETH:
            - prediction[0]: Amount staked for the price going up.
            - prediction[1]: Total stake amount.
    @note
        The probability of the price going up is determined by dividing
        prediction[0] by prediction[1]. The magnitude of stake amounts indicates
        the confidence of the prediction. Ensure stake amounts
        are sufficiently large to be considered meaningful.
    """
    pred_nom, pred_denom = prediction
    print(f"      {feed} has a new prediction: {pred_nom} / {pred_denom}.")
    # Trade here
    # ...

The problem

Look at the bottom of do_trade(). It doesn't actually do any trading yet. Not even the simplest possible trading strategy: "buy if prediction is up; exit 5 min later".

We expect >1 trading strategies over time.

Predictoor bots handle this by having "approach1", "approach2", etc. We could do the same for trader bots.

DoD

• Implement predictoor/trader/approach1/, where it implements do_trade() with the trading strategy: "buy if prediction is up; exit 5 min later".
• Have good unit tests
• Test that it works for real on mainnet

Related issues

• pdr-backend#231 used to have "add strategy" plus "do backtesting". But 271 (this issue) does that. So 231 was de-scoped to just "do backtesting"