Add Key Vault approach for client secret

[guardrex]

Description

I'll probably do this in both the Entra and OIDC articles.

Page URL

https://learn.microsoft.com/en-us/aspnet/core/blazor/security/blazor-web-app-with-entra?view=aspnetcore-9.0

Content source URL

https://github.com/dotnet/AspNetCore.Docs/blob/main/aspnetcore/blazor/security/blazor-web-app-with-entra.md

Document ID

58758d13-94c9-e208-e0f6-16676834413c

Article author

@guardrex