Extra error trapping for Entra BFF sample?

[guardrex]

We might want a bit more error trapping ...

https://github.com/dotnet/blazor-samples/blob/main/9.0/BlazorWebAppEntraBff/BlazorWebAppEntra/Program.cs#L153-L155

@halter73 @mikekistler Does adding ReplyForbiddenWithWwwAuthenticateHeaderAsync trapping on MicrosoftIdentityWebChallengeUserException and MsalUiRequiredException make sense to roll into ☝️ of the Entra BFF sample?

Something like ...

string accessToken;

try
{
    accessToken = await tokenAcquisition.GetAccessTokenForUserAsync(
        scopes, user: httpContext.User);
}
catch (MicrosoftIdentityWebChallengeUserException exception)
{
    await tokenAcquisition.ReplyForbiddenWithWwwAuthenticateHeaderAsync(
        exception.Scopes, exception.MsalUiRequiredException, httpContext.Response);
    return;
}
catch (MsalUiRequiredException exception)
{
    await tokenAcquisition.ReplyForbiddenWithWwwAuthenticateHeaderAsync(
        scopes, exception, httpContext.Response);
    return;
}

if (!string.IsNullorEmpty(accessToken))
{
    transformContext.ProxyRequest.Headers.Authorization = new("Bearer", accessToken);
}

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• Content Source: dotnet/blazor-samples
• GitHub Login: @guardrex