fix(generic): use serializer_factory even with custom serializers

This allows projects to use custom generic serializers that do not have
a `Meta.model` set.

apis_core/generic/api_views.py

@@ -1,5 +1,5 @@
 from rest_framework import viewsets
-from .serializers import serializer_factory
+from .serializers import serializer_factory, GenericHyperlinkedModelSerializer
 from .helpers import first_match_via_mro
 
 
@@ -23,7 +23,8 @@ def get_queryset(self):
         return queryset or self.model.objects.all()
 
     def get_serializer_class(self):
-        serializer_class = first_match_via_mro(
-            self.model, path="serializers", suffix="Serializer"
-        ) or serializer_factory(self.model)
-        return serializer_class
+        serializer_class = (
+            first_match_via_mro(self.model, path="serializers", suffix="Serializer")
+            or GenericHyperlinkedModelSerializer
+        )
+        return serializer_factory(self.model, serializer=serializer_class)

apis_core/generic/serializers.py

@@ -39,7 +39,9 @@ class GenericHyperlinkedModelSerializer(HyperlinkedModelSerializer):
 def serializer_factory(
     model, serializer=GenericHyperlinkedModelSerializer, fields="__all__", **kwargs
 ):
-    meta = type(str("Meta"), (object,), {"model": model, "fields": fields})
+    defaultmeta = type(str("Meta"), (object,), {"fields": fields})
+    meta = getattr(serializer, "Meta", defaultmeta)
+    meta.model = model
     serializer = type(
         str("%sModelSerializer" % model._meta.object_name),
         (serializer,),