Securing Function App via 'Authentication' blade in Azure Portal vs. manually in Startup.cs

[NejcBW]

I secured my function app by modifying the configuration in Startup.cs and calling the AddAuthentiction and AddMicrosoftIdentityWebApi extension methods on the services collection object (similar to the approach used in the 'AzureFunctions' example in the 'Tests' directory). This allows me to securely call the api from my Blazor Server app. The app does not call any downstream api.

This approach works perfectly fine without the need to enable the 'Authentication' option under 'Function App - Setting' in Azure Portal and specifying an identity provider there and linking it to an Azure AD app registration.

Does somebody know what does enabling authentication and adding an identity provider under settings of the Function App in the Azure Portal do compared to the manual configuration in Startup.cs? If I understand correctly, it does the same thing but implicitly instead of explicitly in the Startup.cs.