The classic Authentication / Authorization experience in Azure Function apps will be removed from the Microsoft Azure portal in December 2021. As a result of a lack of Microsoft documentation, we don't know currently what side effects this change will bring to the way how authentication will be handled for Azure Function apps that remain in the old model. To avoid potential issues, I've followed the Microsoft instructions and upgraded to the new authentication experience. For more details, see how to configure your Azure Function app to use Azure Active Directory login.
The following steps describe how I upgraded from the classic authentication experience in a secured Azure Function app:
1. Go to the Azure portal > Your secured Azure Function app > Authentication
2. If the Authentication page shows a warning indicating that the classic Authentication experience will be removed and it includes an Upgrade button, it means that the classic Authentication experience is still in use: