admin objects filtered with tenant mixin

[aleemnazer]

Tenant model should be like this to handle admin objects filtering in admin panel.

class TenantModel(TenantModelMixin, models.Model):
    # Abstract model which all the models related to tenant inherit.

    **admin_objects = models.Manager()**
    objects = TenantManager()

    class Meta:
        abstract = True

[stevelukis]

I don't think this will work if the database engine is set as django_multitenant.backends.postgresql.