Update all involved tests. Also extend model_form_data to
accept an argument `form_kwargs` to pass to form.

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This custom factory subclasses factory.Factory,
and overrides the build method, so that the model_class
gets called with a dict of fields, instead of with keyword
arguments. This is the way Django form classes require data to be
passed to __init__.

This function helps to create form data from models.
See example given.