Created DefaultChallengeScheme on CAP.DashboardOptions.cs to specify dashboard auth challenge scheme (#815)

samples/Sample.RabbitMQ.Postgres.DashboardAuth/Startup.cs

@@ -62,6 +62,7 @@ namespace Sample.RabbitMQ.Postgres.DashboardAuth
                 cap.UseDashboard(d =>
                 {
                     d.UseChallengeOnAuth = true;
+                    d.DefaultChallengeScheme = OpenIdConnectDefaults.AuthenticationScheme;
                     d.Authorization = new[] {new HttpContextDashboardFilter()};
                 });
             });

src/DotNetCore.CAP.Dashboard/CAP.DashboardMiddleware.cs

@@ -136,7 +136,7 @@ namespace DotNetCore.CAP
 
                     if (_options.UseChallengeOnAuth)
                     {
-                        await context.ChallengeAsync();
+                        await context.ChallengeAsync(_options.DefaultChallengeScheme);
                         return;
                     }
 

src/DotNetCore.CAP.Dashboard/CAP.DashboardOptions.cs

@@ -3,6 +3,7 @@
 
 using System.Collections.Generic;
 using DotNetCore.CAP.Dashboard;
+using Microsoft.AspNetCore.Authentication.Cookies;
 
 // ReSharper disable once CheckNamespace
 namespace DotNetCore.CAP
@@ -18,6 +19,11 @@ namespace DotNetCore.CAP
             UseChallengeOnAuth = false;
         }
 
+        /// <summary>
+        /// Default ChallengeScheme used for Dashboard authentication. If no scheme is set, the DefaultScheme set up in AddAuthentication will be used.
+        /// </summary>
+        public string DefaultChallengeScheme { get; set; }
+        
         /// <summary>
         /// Indicates if executes a Challenge for Auth within ASP.NET middlewares
         /// </summary>