Port 'missing field' error fix to C#

src/ApiService/ApiService/OneFuzzTypes/Model.cs

@@ -1002,6 +1002,7 @@ Uri HeartbeatQueue
     // Deprecated. Retained for processing old table data.
     public string? CoverageFilter { get; set; }
 
+    public bool? PreserveExistingOutputs { get; set; }
     public string? ModuleAllowlist { get; set; }
     public string? SourceAllowlist { get; set; }
     public string? TargetAssembly { get; set; }

src/ApiService/ApiService/onefuzzlib/Config.cs

@@ -247,6 +247,10 @@ await _containers.GetContainerSasUrl(x.Item2.Name, StorageType.Corpus, ConvertPe
             config.CheckFuzzerHelp = task.Config.Task.CheckFuzzerHelp ?? true;
         }
 
+        if (definition.Features.Contains(TaskFeature.PreserveExistingOutputs)) {
+            config.PreserveExistingOutputs = task.Config.Task.PreserveExistingOutputs ?? false;
+        }
+
         if (definition.Features.Contains(TaskFeature.ReportList)) {
             config.ReportList = task.Config.Task.ReportList;
         }

src/ApiService/ApiService/onefuzzlib/Defs.cs

@@ -405,6 +405,7 @@ public static class Defs {
         TaskFeature.TargetEnv,
         TaskFeature.TargetOptions,
         TaskFeature.CheckFuzzerHelp,
+        TaskFeature.PreserveExistingOutputs,
      },
      Vm: new VmDefinition(Compare: Compare.Equal, Value: 1),
      Containers: new[] {