test: Make internal types accessible to NSubstitute

tests/Directory.Build.props

@@ -43,6 +43,11 @@
     <EmbeddedResource Include="**\Data\**" />
   </ItemGroup>
 
+  <ItemGroup>
+    <!-- For NSubstitute -->
+    <InternalsVisibleTo Include="DynamicProxyGenAssembly2" />
+  </ItemGroup>
+
   <ItemGroup>
     <!-- From https://github.com/dotnet/msbuild/pull/6285 -->
     <AssemblyAttribute Include="NUnit.Framework.ParallelizableAttribute">

tests/Recyclarr.Core.Tests/Config/Parsing/PostProcessing/ConfigMerging/YamlIncludeResolverTest.cs

@@ -10,11 +10,11 @@ namespace Recyclarr.Core.Tests.Config.Parsing.PostProcessing.ConfigMerging;
 [SuppressMessage("ReSharper", "MemberCanBePrivate.Global")]
 internal sealed class YamlIncludeResolverTest
 {
-    private abstract class TestYamlInclude1 : IYamlInclude;
+    internal abstract class TestYamlInclude1 : IYamlInclude;
 
-    private abstract class TestYamlInclude2 : IYamlInclude;
+    internal abstract class TestYamlInclude2 : IYamlInclude;
 
-    private abstract class TestYamlInclude3 : IYamlInclude;
+    internal abstract class TestYamlInclude3 : IYamlInclude;
 
     [Test, AutoMockData]
     public void Find_and_return_processor(