OAuth w/ external user fix

Author: Weves

backend/onyx/auth/users.py

@@ -493,11 +493,13 @@ async def oauth_callback(
             # Handle case where user has used product outside of web and is now creating an account through web
             if not user.role.is_web_login():
                 # We must use the existing user in the session if it matches
-                # the user we just got by email/oauth
-                if user.id:
-                    user_by_session = await db_session.get(User, user.id)
-                    if user_by_session:
-                        user = user_by_session
+                # the user we just got by email/oauth. Note that this only applies
+                # to multi-tenant, due to the overwriting of the user_db
+                if MULTI_TENANT:
+                    if user.id:
+                        user_by_session = await db_session.get(User, user.id)
+                        if user_by_session:
+                            user = user_by_session
 
                 await self.user_db.update(
                     user,