Make loopback handler more flexible

Make the loopback redirect HTTP handler more flexible by allowing the parameters for the callback to be customised.
This removes the need to use subclasses for certain test scenarios.

Author: martincostello

test/AspNet.Security.OAuth.Providers.Tests/AspNet.Security.OAuth.Providers.Tests.csproj

@@ -5,7 +5,7 @@
     <TargetFrameworks>netcoreapp3.1</TargetFrameworks>
     <IsPackable>false</IsPackable>
     <IsTestProject>true</IsTestProject>
-    <NoWarn>$(NoWarn);CA1707</NoWarn>
+    <NoWarn>$(NoWarn);CA1707;CA2227</NoWarn>
   </PropertyGroup>
 
   <ItemGroup>

test/AspNet.Security.OAuth.Providers.Tests/Infrastructure/LoopbackRedirectHandler.cs

@@ -16,8 +16,10 @@ namespace AspNet.Security.OAuth.Infrastructure
     /// <summary>
     /// A delegating HTTP handler that loops back HTTP requests to external login providers to the local sign-in endpoint.
     /// </summary>
-    internal class LoopbackRedirectHandler : DelegatingHandler
+    public class LoopbackRedirectHandler : DelegatingHandler
     {
+        public IDictionary<string, string> LoopbackParameters { get; set; } = new Dictionary<string, string>();
+
         public HttpMethod RedirectMethod { get; set; } = HttpMethod.Get;
 
         public IDictionary<string, string> RedirectParameters { get; set; } = new Dictionary<string, string>();
@@ -110,6 +112,14 @@ protected virtual Uri BuildLoopbackUri(HttpResponseMessage responseMessage)
                 queryString.Add(OAuthStateKey, oauthState);
             }
 
+            if (LoopbackParameters?.Count > 0)
+            {
+                foreach (var parameter in LoopbackParameters)
+                {
+                    queryString[parameter.Key] = parameter.Value;
+                }
+            }
+
             builder.Query = queryString.ToString();
 
             return builder.Uri;

test/AspNet.Security.OAuth.Providers.Tests/OAuthTests`1.cs

@@ -126,7 +126,7 @@ protected WebApplicationFactory<Program> CreateTestServer(Action<IServiceCollect
         protected HttpClient CreateBackchannel(AuthenticationBuilder builder)
             => builder.Services.BuildServiceProvider().GetRequiredService<IHttpClientFactory>().CreateClient();
 
-        public DelegatingHandler LoopbackRedirectHandler { get; set; }
+        public LoopbackRedirectHandler LoopbackRedirectHandler { get; set; }
 
         /// <summary>
         /// Run the ChannelAsync for authentication

test/AspNet.Security.OAuth.Providers.Tests/Shopify/ShopifyLoopbackRedirectHandler.cs

@@ -22,12 +22,7 @@ public class ShopifyTests : OAuthTests<ShopifyAuthenticationOptions>
         public ShopifyTests(ITestOutputHelper outputHelper)
         {
             OutputHelper = outputHelper;
-
-            LoopbackRedirectHandler = new ShopifyLoopbackRedirectHandler()
-            {
-                RedirectUri = RedirectUri,
-                ShopName = TestShopName
-            };
+            LoopbackRedirectHandler.LoopbackParameters.Add("shop", "apple.myshopify.com");
         }
 
         public override string DefaultScheme => ShopifyAuthenticationDefaults.AuthenticationScheme;