12794 change User ref to get_user_model (#12905)

* 12794 change User ref to get_user_model

* 12794 call get_user_model once in tests

* 12794 call get_user_model once in tests

* 12794 use settings.AUTH_USER_MODEL for FK reference

netbox/extras/tests/test_api.py

@@ -1,6 +1,6 @@
 import datetime
 
-from django.contrib.auth.models import User
+from django.contrib.auth import get_user_model
 from django.contrib.contenttypes.models import ContentType
 from django.urls import reverse
 from django.utils.timezone import make_aware
@@ -15,6 +15,9 @@ from extras.scripts import BooleanVar, IntegerVar, Script, StringVar
 from utilities.testing import APITestCase, APIViewTestCases
 
 
+User = get_user_model()
+
+
 class AppTest(APITestCase):
 
     def test_root(self):