Use serializer context in virtual model

[jackson541]

Hello!
This PR is opened to implement the suggestion of issue #33

How mentioned in the issue, the main change in the code was passes the serializer context to virtual model using a new param, that is catch by de kwargs:

    virtual_model_instance = virtual_model(
        user=self.get_request_user(), serializer_context=self.context
    )

https://github.com/jackson541/django-virtual-models/blob/ee215926e9ae5c093f7b25f630f9ce6ab8d03323/django_virtual_models/serializers.py#L77-L79

A new file of tests to Virtual Model Serializers was created to check this implementation.

Thanks for the attention! 😄

[fjsj]

Sorry for the late response, but thanks! I will review and merge that soon.

[fjsj]

Sorry for the late merge. Merging now and releasing soon!

[jackson541]

Everything is fine. Thanks for the merge!