Redesigning existing DB

Hello,

I have an existing django project. The models have to be redesigned and tests written for models.
It is a supplier and resources DB. There needs to be SupplierResource table so that I can bring all the supplier related resources. I want to avoid using the polymorphism.
Here are example models:

class Supplier(models.Model):
delivery_time = models.CharField(max_length=255, blank=True, null=True)
minimum_order_quantity = models.FloatField(blank=True, null=True)
billing_address = models.ForeignKey(...)
shipping_address = models.ForeignKey(...)
# ...


class Resource(models.Model):
code = models.CharField(max_length=255, unique=True, blank=True, null=True)
supplier = models.ForeignKey(
Company,
related_name="supplier_part",
on_delete=models.SET_NULL,
null=True,
blank=True,
)
country = models.CharField(max_length=255, blank=True, null=True)
class Meta:
abstract = True

class Fabric(Resource):
some_attr = models.CharField(max_length=255, blank=True, null=True)


class Ink(Resource):
some_other_attr = models.CharField(max_length=255, blank=True, null=True)