exclude_none parameter in session.save

[Oliversinn]

I know is very useful to save all of the fields in database because that makes each document to contain all the fields of the model. But something that I liked about Pydantic when I wasn't using ODMantic, is the fact that they have the option in model_dump to exclude all the fields that are None with the parameter exclude_none. In my situation we are looking to have documents in database without fields set to null. It would be nice if I could have the option to do so with ODMantic as well.