Remove Missing Constraints logic

- remove logic
- reomove tests

src/MediatR/Registration/ServiceRegistrar.cs

@@ -228,10 +228,7 @@ private static (Type Service, Type Implementation) GetConcreteRegistrationTypes(
         var constraintsForEachParameter = openRequestHandlerImplementation
             .GetGenericArguments()
             .Select(x => x.GetGenericParameterConstraints())
-            .ToList();
-
-        if (constraintsForEachParameter.Count > 2 && constraintsForEachParameter.Any(constraints => !constraints.Where(x => x.IsInterface || x.IsClass).Any()))
-            throw new ArgumentException($"Error registering the generic handler type: {openRequestHandlerImplementation.FullName}. When registering generic requests with more than two type parameters, each type parameter must have at least one constraint of type interface or class.");
+            .ToList();
 
         var typesThatCanCloseForEachParameter = constraintsForEachParameter
             .Select(constraints => assembliesToScan

test/MediatR.Tests/GenericRequestHandlerTests.cs

@@ -93,24 +93,6 @@ public void ShouldNotRegisterDuplicateHandlers(int numberOfClasses, int numberOf
             hasDuplicates.ShouldBeFalse();
         }
 
-        [Fact]
-        public void ShouldThrowExceptionWhenRegisterningHandlersWithNoConstraints()
-        {
-            IServiceCollection services = new ServiceCollection();
-            services.AddSingleton(new Logger());
-
-            var assembly = GenerateMissingConstraintsAssembly();
-
-            Should.Throw<ArgumentException>(() =>
-            {
-                services.AddMediatR(cfg =>
-                {
-                    cfg.RegisterServicesFromAssembly(assembly);
-                });
-            })
-            .Message.ShouldContain("When registering generic requests with more than two type parameters, each type parameter must have at least one constraint of type interface or class.");
-        }
-
         [Fact]
         public void ShouldThrowExceptionWhenTypesClosingExceedsMaximum()
         {

test/MediatR.Tests/MicrosoftExtensionsDI/BaseGenericRequestHandlerTests.cs

@@ -9,11 +9,7 @@
 namespace MediatR.Tests.MicrosoftExtensionsDI
 {
     public abstract class BaseGenericRequestHandlerTests
-    {      
-
-        protected static Assembly GenerateMissingConstraintsAssembly() =>
-           CreateAssemblyModuleBuilder("MissingConstraintsAssembly", 3, 3, CreateHandlerForMissingConstraintsTest);
-
+    { 
         protected static Assembly GenerateTypesClosingExceedsMaximumAssembly() =>
             CreateAssemblyModuleBuilder("ExceedsMaximumTypesClosingAssembly", 201, 1, CreateHandlerForExceedsMaximumClassesTest);