Support custom OAuth provider with Federated Identity Credential

**Is your feature request related to a problem? Please describe.**

Could you please support using Federated Identity Credential to configure a custom OAuth provider for a SWA? Our tenant policy prohibits creating any client secrets, but it seems to be what most tutorials are refering to.

**Describe the solution you'd like**

Support using Federated Identity Credential to configure a custom OAuth provider for a SWA.

**Describe alternatives you've considered**

I attempted to use a custom certificate to configure the custom OAuth provider but I wasn't able to get it to work. I followed the instructions in https://learn.microsoft.com/en-us/azure/static-web-apps/authentication-custom?tabs=aad%2Cfunction#custom-certificate. After configuring my custom OAuth provider, I visited my site, signs in, and get a 401 at the login callback page. I don't know what to do next. Unfortunately, there aren't enough documentations or examples online on how to use a certificate for the custom OAuth provider. Besides, given that certificate share many common issues in client secrets, using Federated Identity Credential is still a more ideal solution.

**Additional context**

N/A