Demonstrate issue 3233 (graphql-dotnet#3256)

Author: sungam3r

src/GraphQL.Tests/Bugs/Issue3233.cs

@@ -0,0 +1,29 @@
+namespace GraphQL.Tests.Bugs;
+
+public class Issue3233
+{
+    [Fact]
+    public void Throws_NotSupportedException_On_Object_Key()
+    {
+        var serializer = new SystemTextJson.GraphQLSerializer();
+        var result = new ExecutionResult();
+        result.AddError(new ExecutionError("oops1"));
+        var serialized = serializer.Serialize(result);
+        serialized.ShouldBe("{\"errors\":[{\"message\":\"oops1\"}]}");
+
+        result = new ExecutionResult();
+        var errorWithData = new ExecutionError("oops2");
+        errorWithData.Data.Add(new object(), "WOW");
+        result.AddError(errorWithData);
+
+        var ex = Should.Throw<NotSupportedException>(() => serializer.Serialize(result));
+        var messages = new[]
+        {
+            "The type 'System.Object' is not a supported Dictionary key type. Path: $.",
+            "The type 'System.Object' is not a supported dictionary key using converter of type 'System.Text.Json.Serialization.Converters.ObjectConverter'. Path: $.",
+            "The collection type 'System.Collections.ListDictionaryInternal' is not supported."
+        };
+        if (!messages.Contains(ex.Message))
+            throw ex;
+    }
+}