Seal/abstract/virtual everything (#6739)

Content.Server/NodeContainer/NodeGroups/NodeGroupFactory.cs

@@ -21,7 +21,7 @@ namespace Content.Server.NodeContainer.NodeGroups
         INodeGroup MakeNodeGroup(NodeGroupID id);
     }
 
-    public class NodeGroupFactory : INodeGroupFactory
+    public sealed class NodeGroupFactory : INodeGroupFactory
     {
         [Dependency] private readonly IReflectionManager _reflectionManager = default!;
         [Dependency] private readonly IDynamicTypeFactory _typeFactory = default!;