How to configure HttpClient to use Default System Proxy

[john]

Some details

In this doc https://microsoft.github.io/reverse-proxy/articles/http-client-config.html#httpclient is shows a way to configure a WebProxy, but not mention how to just set the HttpClientHandler.UseProxy to true,
I use a custom configuration to set it to use system proxy for fiddler debugging

                .ConfigureHttpClient((c, h) =>
                {
                    
                    h.UseProxy = true;
                })

and I hope I can use the build in configuration for that

[Miha Zupan]

This seems like something we could call out in the docs - The default ForwarderHttpClientFactory will set UseProxy to false, so if you want to use the default proxy (not a manually specified one from the config), you can flip it back to true.

Another similar case with fiddler: #1477 (comment)

I don't remember actually discussing why the default of disabling UseProxy was chosen though.