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_views.py

@@ -1,7 +1,7 @@
 import urllib.parse
 import uuid
 
-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
 
@@ -11,6 +11,9 @@ from extras.models import *
 from utilities.testing import ViewTestCases, TestCase
 
 
+User = get_user_model()
+
+
 class CustomFieldTestCase(ViewTestCases.PrimaryObjectViewTestCase):
     model = CustomField