Extending global filter set overrides

[an0o0nym]

Is your feature request related to a problem? Please describe.
I am generating DjangoObjectType from my models dynamically. Some of those models have custom model fields that I have defined in my project. This throws an error i.e.:

AssertionError: MyModelSet resolved field 'custom' with 'exact' lookup to an unrecognized field type CustomField. Try adding an override to 'Meta.filter_overrides'. See: https://django-filter.readthedocs.io/en/master/ref/filterset.html#customise-filter-generation-with-filter-overrides

Describe the solution you'd like
I would like to be able to extend global filterset overrides for those custom fields just like graphene-django does with GRAPHENE_FILTER_SET_OVERRIDES. Doing this by manually extending GrapheneFilterSetMixin.FILTER_DEFAULTS seems to work for my case.

I think this solution does not cause any backward incompatibility nor introduce any complexity. The solution is pretty easy to understand and introduce to the project code base. I hope this will add more flexibility to the project for future users facing similar problems.

class GrapheneFilterSetMixin(BaseFilterSet):
    """ A django_filters.filterset.BaseFilterSet with default filter overrides
    to handle global IDs """

    FILTER_DEFAULTS = dict(
        itertools.chain(
            FILTER_FOR_DBFIELD_DEFAULTS.items(), 
            GRAPHENE_FILTER_SET_OVERRIDES.items(), 
            getattr(settings, 'EXTRA_FILTER_SET_OVERRIDES', {}).items()
        )
    )

Describe alternatives you've considered
An alternative I have used before developing above solution was to quickly monkey patch solution, however this did not seem to work not to mention is not a long-time solution.