Object handles: add support for Pydantic models, (data)classes & plots

[fzumstein]

As a starting point, converting to dict already works:

def test_pydantic_model():
    from pydantic import BaseModel
    
    class MyModel(BaseModel, arbitrary_types_allowed=True):
        a: str
        d: dict
        df: pd.DataFrame
    mymodel = MyModel(a="b", d={"a": 1}, df=pd.DataFrame({"a": [1], "b": [2]}))
    mymodel2 = MyModel.model_validate(deserialize(serialize(dict(mymodel))))
    assert mymodel.a == mymodel2.a
    assert mymodel.d == mymodel2.d
    assert_frame_equal(mymodel.df, mymodel2.df)


def test_dataclass():
    from dataclasses import dataclass

    @dataclass
    class MyDataClass:
        a: str
        d: dict
        df: pd.DataFrame

    mydataclass = MyDataClass(a="b", d={"a": 1}, df=pd.DataFrame({"a": [1], "b": [2]}))
    mydataclass2 = MyDataClass(**deserialize(serialize(mydataclass.__dict__)))
    assert mydataclass.a == mydataclass2.a
    assert mydataclass.d == mydataclass2.d
    assert_frame_equal(mydataclass.df, mydataclass2.df)