ordering_filters not recognized when i extend OrderingFilter class

[Simha Rupa Das]

I want to have a case-insensitive orderingfilter for name field so i have created a class CaseInsensitiveOrderingFilter which extends OrderingFilter:

```

class CaseInsensitiveOrderingFilter(OrderingFilter):

ordering_fields = ('name')

def filter_queryset(self, request, queryset, view):

ordering = self.get_ordering(request, queryset, view)

if ordering:

new_ordering = []

for field in ordering:

if field.startswith('-'):

new_ordering.append(Lower(field[1:]).desc())

else:

new_ordering.append(Lower(field).asc())

return queryset.order_by(*new_ordering)

return queryset

```

and then use it in the ListApiView

```

class IngredientListAPIView(ListAPIView):

queryset = Ingredient.objects.all()

serializer_class = IngredientListSerializer

filter_backends = [SearchFilter,CaseInsensitiveOrderingFilter]

```

then i try the endpoint:

http://127.0.0.1:8000/api/ingredients/?ordering=-name

It does not sort the queryset w.r.t name field.

When i debig I found that: 

```

           fields = [param.strip() for param in params.split(',')]  -- ['name]

           ordering = self.remove_invalid_fields(queryset, fields, view)  ---- []

```

why ordering = []

where as removing ordering_filters inside CaseInsensitiveOrderingFilter, sorts any field with CaseInsensitiveOrderingFilter

```

class CaseInsensitiveOrderingFilter(OrderingFilter):

### ordering_fields = ('name')

print(ordering_fields)

def filter_queryset(self, request, queryset, view):

ordering = self.get_ordering(request, queryset, view)

if ordering:

new_ordering = []

for field in ordering:

if field.startswith('-'):

new_ordering.append(Lower(field[1:]).desc())

else:

new_ordering.append(Lower(field).asc())

return queryset.order_by(*new_ordering)

return queryset

```

HOw to pass the ordering_fields to the extended class of OrderingFilter