Custom fields to list-serializer init

[sevdog]

As of now it is possible to provide custom init arguments to a model serializer if the __init__ method is overridden. However it is not possible to provide any custom init argument to a list serializer without overriding the many_init method:

django-rest-framework/rest_framework/serializers.py

Lines 150 to 165 in df92e57

	list_kwargs = {
	'child': child_serializer,
	}
	if allow_empty is not None:
	list_kwargs['allow_empty'] = allow_empty
	if max_length is not None:
	list_kwargs['max_length'] = max_length
	if min_length is not None:
	list_kwargs['min_length'] = min_length
	list_kwargs.update({
	key: value for key, value in kwargs.items()
	if key in LIST_SERIALIZER_KWARGS
	})
	meta = getattr(cls, 'Meta', None)
	list_serializer_class = getattr(meta, 'list_serializer_class', ListSerializer)
	return list_serializer_class(*args, **list_kwargs)

In a case there should be some kind of custom validation logic which may depends from a custom param provided in init at the moment the only way to use this is to "proxy" self.child properties since no custom param will ever get passed to the list serializer.

It could make sense to have an attribute in ListSerializer from which add kwargs to list serializer (or to control which kwargs will be received only by the list serializer).