adding the option of defining a filterset_class in the Meta class

Author: ecbakosl

graphene_django/filter/fields.py

@@ -48,7 +48,11 @@ def args(self, args):
 
     @property
     def filterset_class(self):
-        return get_filterset_class(self._filterset_class, **self.meta)
+        if self.node_type()._meta.filterset_class:
+            filterset_class = self.node_type()._meta.filterset_class
+        else:
+            filterset_class = get_filterset_class(self._filterset_class, **self.meta)
+        return filterset_class
 
     @property
     def filtering_args(self):

graphene_django/types.py

@@ -58,7 +58,8 @@ def __new__(cls, name, bases, attrs):
             only_fields=(),
             exclude_fields=(),
             interfaces=(),
-            registry=None
+            registry=None,
+            filterset_class=None
         )
         if DJANGO_FILTER_INSTALLED:
             # In case Django filter is available, then