Upgraded to dotnetcore 3.1

as per migration recommendations

sample/MongoIdentitySample.Mvc/Startup.cs

@@ -1,15 +1,15 @@
-using System;
+using AspNetCore.Identity.MongoDbCore.Infrastructure;
+using AspNetCore.Identity.MongoDbCore.Models;
 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Identity;
+using Microsoft.Extensions.Hosting;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
-using Microsoft.Extensions.Logging;
 using MongoIdentitySample.Mvc.Models;
 using MongoIdentitySample.Mvc.Services;
-using AspNetCore.Identity.MongoDbCore.Models;
-using Microsoft.AspNetCore.Identity;
-using AspNetCore.Identity.MongoDbCore.Infrastructure;
-using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging;
+using System;
 
 namespace MongoIdentitySample.Mvc
 {
@@ -24,12 +24,6 @@ namespace MongoIdentitySample.Mvc
                 //per user config that is not committed to repo, use this to override settings (e.g. connection string) based on your local environment.
                 .AddJsonFile($"appsettings.local.json", optional: true); 
 
-            if (env.IsDevelopment())
-            {
-                // For more details on using the user secret store see https://go.microsoft.com/fwlink/?LinkID=532709
-                builder.AddUserSecrets<Startup>();
-            }
-
             builder.AddEnvironmentVariables();
             Configuration = builder.Build();
         }
@@ -44,8 +38,10 @@ namespace MongoIdentitySample.Mvc
             var settings = Configuration.GetSection(nameof(MongoDbSettings)).Get<MongoDbSettings>();
 
             services.AddSingleton<MongoDbSettings>(settings);
+            
             services.AddIdentity<ApplicationUser, MongoIdentityRole>()
                     .AddMongoDbStores<ApplicationUser, MongoIdentityRole, Guid>(settings.ConnectionString, settings.DatabaseName)
+                    .AddSignInManager()
                     .AddDefaultTokenProviders();
 
             services.AddMvc();
@@ -58,11 +54,8 @@ namespace MongoIdentitySample.Mvc
         }
 
         // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
-        public void Configure(IApplicationBuilder app, IWebHostEnvironment env) //, ILoggerFactory loggerFactory)
+        public void Configure(IApplicationBuilder app, IWebHostEnvironment env, ILoggerFactory loggerFactory)
         {
-            //loggerFactory.AddConsole(Configuration.GetSection("Logging"));
-            //loggerFactory.AddDebug();
-
             if (env.IsDevelopment())
             {
                 app.UseDeveloperExceptionPage();
@@ -73,16 +66,17 @@ namespace MongoIdentitySample.Mvc
                 app.UseExceptionHandler("/Home/Error");
             }
 
-            app.UseRouting();
             app.UseStaticFiles();
-            
+
+            app.UseRouting();
+
             app.UseAuthentication();
             app.UseAuthorization();
-            // Add external authentication middleware below. To configure them please see https://go.microsoft.com/fwlink/?LinkID=532715
 
             app.UseEndpoints(endpoints =>
             {
                 endpoints.MapDefaultControllerRoute();
+                endpoints.MapRazorPages();
             });
         }
     }