cmsmanage/paperwork/routers.py

class PaperworkRouter:
    app_label = "paperwork"
    related_app_labels = {"paperwork", "membershipworks"}
    db = "cms"

    def db_for_read(self, model, **hints):
        if model._meta.app_label == self.app_label:
            return self.db
        return None

    def db_for_write(self, model, **hints):
        if model._meta.app_label == self.app_label:
            return self.db
        return None

    def allow_relation(self, obj1, obj2, **hints):
        if (
            obj1._meta.app_label in self.related_app_labels
            or obj2._meta.app_label in self.related_app_labels
        ):
            return True
        return None