Improve IHttpClient factories (#20)

Codestyle fixes
Setup CODEOWNERS
Setup dependabot

SystemExtensions.DependencyInjection.Tests/Http/Models/HttpMessageHandlerMock.cs

@@ -0,0 +1,16 @@
+using System.Net.Http;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace SystemExtensions.NetStandard.DependencyInjection.Tests.Http.Models;
+public sealed class HttpMessageHandlerMock : HttpMessageHandler
+{
+    public bool Called { get; private set; }
+
+    protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
+    {
+        this.Called = true;
+
+        return Task.FromResult(new HttpResponseMessage());
+    }
+}