Ipaddress model does not accept null value for role, but serializer does (regression in 3.5-beta)

[amhn]

NetBox version

v3.5-beta

Python version

3.10

Steps to Reproduce

1. POST the following to /api/ipam/ip-addresses/:

{
  "address": "127.0.0.2/8",
  "status": "active",
  "role": null
}

Expected Behavior

IP address is created with role = '' (as in 3.4) or role = null

Observed Behavior

Internal Server Error: /api/ipam/ip-addresses/
Traceback (most recent call last):
  File "/home/andy/python/netbox/venv/lib/python3.10/site-packages/django/db/backends/utils.py", line 89, in _execute
    return self.cursor.execute(sql, params)
psycopg2.errors.NotNullViolation: null value in column "role" of relation "ipam_ipaddress" violates not-null constraint
DETAIL:  Failing row contains (2023-04-06 19:31:31.261817+00, 2023-04-06 19:31:31.26183+00, {}, 3, 127.0.0.2/8, active, null, null, , , null, null, null, null, ).

This is caused by adding "allow_null=True" to the role field in IPAddressSerializer in the beta code. Without allow_null the serializer silently changes the null value to '' which does not raise the database exception.

Maybe changing the database field to also allow null values is the best option here since a GET request already returns null for an empty ('') value in the database.