runtime: AddJwtBearer doesn't consider system proxy settings

Description

When we have an Authority to validate the access token and environment variables for proxy settings have been defined (HTTP_PROXY, HTTPS_PROXY, NO_PROXY), the HttpClient which is responsible to make a request to the Authority url seems doesn’t consider system proxy settings.

Reproduction Steps

    builder.Services
      .AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
      .AddJwtBearer(JwtBearerDefaults.AuthenticationScheme, options =>
        {
          options.Authority = JWT_AUTHORITY;
          options.SaveToken = true;
          options.TokenValidationParameters = new TokenValidationParameters
          {
            ValidateIssuer = false,
            ValidateAudience = false,
            RequireAudience = false,
          };
        }
      );

Expected behavior

The request should be successful.

Actual behavior

System.InvalidOperationException: IDX20803: Unable to obtain configuration from: '[PII of type 'System.String' is hidden. For more details, see https://aka.ms/IdentityModel/PII.]'.
 ---> System.IO.IOException: IDX20804: Unable to retrieve document from: '[PII of type 'System.String' is hidden. For more details, see https://aka.ms/IdentityModel/PII.]'.
 ---> System.Net.Http.HttpRequestException: The proxy tunnel request to proxy 'http://proxy.site.net:8080/' failed with status code '503'."
   at System.Net.Http.HttpConnectionPool.EstablishProxyTunnelAsync(Boolean async, HttpRequestHeaders headers, CancellationToken cancellationToken)
   at System.Net.Http.HttpConnectionPool.ConnectAsync(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken)
   at System.Net.Http.HttpConnectionPool.CreateHttp11ConnectionAsync(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken)
   at System.Net.Http.HttpConnectionPool.AddHttp11ConnectionAsync(HttpRequestMessage request)
   at System.Threading.Tasks.TaskCompletionSourceWithCancellation`1.WaitWithCancellationAsync(CancellationToken cancellationToken)
   at System.Net.Http.HttpConnectionPool.GetHttp11ConnectionAsync(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken)
   at System.Net.Http.HttpConnectionPool.SendWithVersionDetectionAndRetryAsync(HttpRequestMessage request, Boolean async, Boolean doRequestAuth, CancellationToken cancellationToken)
   at System.Net.Http.DiagnosticsHandler.SendAsyncCore(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken)
   at System.Net.Http.RedirectHandler.SendAsync(HttpRequestMessage request, Boolean async, CancellationToken cancellationToken)
   at System.Net.Http.HttpClient.<SendAsync>g__Core|83_0(HttpRequestMessage request, HttpCompletionOption completionOption, CancellationTokenSource cts, Boolean disposeCts, CancellationTokenSource pendingRequestsCts, CancellationToken originalCancellationToken)
   at Microsoft.IdentityModel.Protocols.HttpDocumentRetriever.GetDocumentAsync(String address, CancellationToken cancel)
   --- End of inner exception stack trace ---
   at Microsoft.IdentityModel.Protocols.HttpDocumentRetriever.GetDocumentAsync(String address, CancellationToken cancel)
   at Microsoft.IdentityModel.Protocols.OpenIdConnect.OpenIdConnectConfigurationRetriever.GetAsync(String address, IDocumentRetriever retriever, CancellationToken cancel)
   at Microsoft.IdentityModel.Protocols.ConfigurationManager`1.GetConfigurationAsync(CancellationToken cancel)
   --- End of inner exception stack trace ---
   at Microsoft.IdentityModel.Protocols.ConfigurationManager`1.GetConfigurationAsync(CancellationToken cancel)
   at Microsoft.AspNetCore.Authentication.JwtBearer.JwtBearerHandler.HandleAuthenticateAsync()
   at Microsoft.AspNetCore.Authentication.JwtBearer.JwtBearerHandler.HandleAuthenticateAsync()
   at Microsoft.AspNetCore.Authentication.AuthenticationHandler`1.AuthenticateAsync()
   at Microsoft.AspNetCore.Authentication.AuthenticationService.AuthenticateAsync(HttpContext context, String scheme)
   at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
   at Company.ExceptionHandlingMiddleware.InvokeAsync(HttpContext context, RequestDelegate next) in

Regression?

No response

Known Workarounds

We had to set the proxy settings directly and it worked

    builder.Services
      .AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
      .AddJwtBearer(JwtBearerDefaults.AuthenticationScheme, options =>
        {
          options.Authority = JWT_AUTHORITY;
          options.BackchannelHttpHandler = new HttpClientHandler
          {
            UseProxy = true,
            Proxy = new WebProxy
            {
              Address = new Uri("http://proxy.site.net:8080"),
              BypassProxyOnLocal = true,
              BypassList = new string[] { "localhost" },
            }
          };
          options.SaveToken = true;
          options.TokenValidationParameters = new TokenValidationParameters
          {
            ValidateIssuer = false,
            ValidateAudience = false,
            RequireAudience = false,
          };
        }
      );

Configuration

• .NET 6.0
• Windows 10 Enterprise
• x64

Other information

No response