[Feature Request] Enable MicrosoftIdentityWebAppAuthenticationBuilder extension methods to configure scheme options

[NetherGranite]

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

It is not possible to write extension methods for the builder returned by .AddMicrosoftIdentityWebApp() (MicrosoftIdentityWebAppAuthenticationBuilder) that configure the OpenID Connect scheme's options because the .OpenIdConnectScheme property has a private getter.

See here:

https://github.com/AzureAD/microsoft-identity-web/blob/15de647e65280299fbec594957213f2d5b5564bf/src/Microsoft.Identity.Web/WebAppExtensions/MicrosoftIdentityWebAppAuthenticationBuilder.cs#L49

For example, it is not possible to write either of these extension methods:

authenticationBuilder.AddMicrosoftIdentityWebApp(options => { }, "MySchemeName")
    .ConfigureClientSecretFromServices()
    .PreventSignIn();

Describe the solution you'd like

Give .OpenIdConnectScheme a public getter.

Describe alternatives you've considered

1. Wrap MicrosoftIdentityWebAppAuthenticationBuilder with a custom class that properly exposes the OpenID Connect scheme that you can then write extension methods for:

authenticationBuilder.AddMicrosoftIdentityWebApp(options => { }, "MySchemeName")
    .WrapWithExtensibleBuilder("MySchemeName")
    .ConfigureClientSecretFromServices()
    .PreventSignIn();

2. Pass the OpenID Connect scheme to every extension method:

authenticationBuilder.AddMicrosoftIdentityWebApp(options => { }, "MySchemeName")
    .ConfigureClientSecretFromServices("MySchemeName")
    .PreventSignIn("MySchemeName");

Both require repeating the OpenID Connect scheme (which worst case is error prone) and unnecessary and potentially confusing extra typing.