Should ProfileDetailView be login_required

Should there be a mechanism to ensure `ProfileDetailView` is only accessible by logged in users?

```
class ProfileDetailView(generics.RetrieveUpdateAPIView):
    model = User
    serializer_class = serializers.ProfileSerializer

    def get_object(self):
        return self.request.user
```

Setting DEFAULT_PERMISSION_CLASSES will ensure it is protected but otherwise  `get_object` to return the `AnonymousUser`!

```
REST_FRAMEWORK = {
    'DEFAULT_PERMISSION_CLASSES': (
        'rest_framework.permissions.IsAuthenticated',
    ),
}
```

any thoughts @meshy @Ian-Foote?