refactor(access): Update all references to User to use get_user_model()

ref: #754 #704 #755

app/access/mixins/organization.py

@@ -1,9 +1,13 @@
-from django.contrib.auth.models import User, Group
+import django
+
+from django.contrib.auth.models import Group
 from django.db import models
 
 from access.models.organization import Organization
 from access.models.team import Team
 
+User = django.contrib.auth.get_user_model()
+
 
 
 class OrganizationMixin: