Address code review feedback

opentech/apply/users/decorators.py

-from django.conf import settings
 from django.core.exceptions import PermissionDenied
 
+from .utils import can_use_oauth_check
+
 
 def require_oauth_whitelist(view_func):
     """Simple decorator that limits the use of OAuth to the configure whitelisted domains"""
     def decorated_view(request, *args, **kwargs):
-        user = request.user
-
-        try:
-            if settings.SOCIAL_AUTH_GOOGLE_OAUTH2_WHITELISTED_DOMAINS:
-                for domain in settings.SOCIAL_AUTH_GOOGLE_OAUTH2_WHITELISTED_DOMAINS:
-                    if user.email.endswith(f'@{domain}'):
-                        return view_func(request, *args, **kwargs)
-        except AttributeError:
-            raise PermissionDenied
+        if can_use_oauth_check(request.user):
+            return view_func(request, *args, **kwargs)
 
         raise PermissionDenied
 

opentech/apply/users/templatetags/users_tags.py

 from django import template
-from django.conf import settings
+
+from ..utils import can_use_oauth_check
 
 register = template.Library()
 
 
 @register.filter
 def backend_name(name):
+    """Human readable mapping for the social auth backend"""
     return {
         'google-oauth': 'Google OAuth',
         'google-oauth2': 'Google OAuth',
         'google-openidconnect': 'Google OpenId',
-        'facebook-app': 'Facebook',
-        'stackoverflow': 'Stack Overflow',
-        'yahoo-oauth': 'Yahoo',
-        'vimeo': 'Vimeo',
-        'linkedin-oauth2': 'LinkedIn OAuth',
-        'vk-oauth2': 'VK OAuth',
-        'live': 'Windows Live',
     }.get(name, name)
 
 
@@ -29,12 +24,4 @@ def backend_class(backend):
 def can_use_oauth(context):
     user = context.get('user')
 
-    try:
-        if settings.SOCIAL_AUTH_GOOGLE_OAUTH2_WHITELISTED_DOMAINS:
-            for domain in settings.SOCIAL_AUTH_GOOGLE_OAUTH2_WHITELISTED_DOMAINS:
-                if user.email.endswith(f'@{domain}'):
-                    return True
-    except AttributeError:
-        return False
-
-    return False
+    return can_use_oauth_check(user)

opentech/apply/users/utils.py

+from django.conf import settings
+
+
+def can_use_oauth_check(user):
+    """
+    Checks that the user belongs to the whitelisted domains.
+    Anonymous or non-whitelisted email domains cannot log in
+    or associate OAuth accounts
+    """
+    try:
+        domain = user.email.split('@')[-1]
+        return domain in settings.SOCIAL_AUTH_GOOGLE_OAUTH2_WHITELISTED_DOMAINS
+    except AttributeError:
+        # Anonymous user or setting not defined
+        pass
+    return False