Can't Use ARIMA Additinal Parameters in arima_boost()

[AlbertoAlmuinha]

Hi @mdancho84 ,

I noticed that the arima_boost function does not allow me to use additional parameters through the set_engine function for the ARIMA model, but sends all additional parameters for the XGBoost model.

Would it be possible to find a solution such as having to use a named list? Maybe in case one of the parameters is a list called "arima" you can take those parameters for the arima function and the rest for XGboost. In case there is no such list, it would continue as before.

[mdancho84]

Sorry just getting back to you. If you are still interested maybe make a PR and we can discuss.