Allow for error result objects when using mutation conventions.

src/HotChocolate/Core/src/Abstractions/AggregateError.cs

@@ -1,7 +1,9 @@
 using System;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
-using HotChocolate.Properties;
+using System.Threading.Tasks;
+using static HotChocolate.Properties.AbstractionResources;
 
 namespace HotChocolate;
 
@@ -17,7 +19,7 @@ public class AggregateError : Error
     /// The errors.
     /// </param>
     public AggregateError(IEnumerable<IError> errors)
-        : base(AbstractionResources.AggregateError_Message)
+        : base(AggregateError_Message)
     {
         if (errors is null)
         {
@@ -34,7 +36,7 @@ public AggregateError(IEnumerable<IError> errors)
     /// The errors.
     /// </param>
     public AggregateError(params IError[] errors)
-        : base(AbstractionResources.AggregateError_Message)
+        : base(AggregateError_Message)
     {
         Errors = errors ?? throw new ArgumentNullException(nameof(errors));
     }

src/HotChocolate/Core/src/Abstractions/IMutationResult.cs

@@ -0,0 +1,17 @@
+namespace HotChocolate;
+
+/// <summary>
+/// This interface allows middleware to access the mutation result value in an generic way.
+/// </summary>
+public interface IMutationResult
+{
+    /// <summary>
+    /// Gets the mutation result value.
+    /// </summary>
+    object Value { get; }
+
+    /// <summary>
+    /// Defines if the mutation was successful and if the result represents a success result.
+    /// </summary>
+    bool IsSuccess { get; }
+}