updated c# syntax to work on older versions of dotnet

Author: Afroz Mohammed

generator/AWSPSGeneratorLib/Utils/Extensions.cs

@@ -60,7 +60,8 @@ public static bool IsSensitive(this PropertyInfo propertyInfo)
         /// </summary>
         public static bool ContainsSensitiveData(this Type type, HashSet<Type> visitedTypes = null)
         {
-            visitedTypes ??= [];
+            if (visitedTypes == null)
+                visitedTypes = new HashSet<Type>();
 
             if (!visitedTypes.Add(type)) 
                 return false;

generator/AWSPSGeneratorLib/Writers/SourceCode/CmdletSourceWriter.cs

@@ -238,12 +238,12 @@ public void Write(IndentedTextWriter writer, string awsSignerAttributeTypeValue)
 
         private void WriteSensitiveDataFlags(IndentedTextWriter writer)
         {
-            if (ContainsSensitiveData(MethodAnalysis.RequestType))
+            if (MethodAnalysis.RequestType.ContainsSensitiveData())
             {
                 writer.WriteLine();
                 writer.WriteLine("protected override bool IsSensitiveRequest { get; set; } = true;");
             }
-            if (ContainsSensitiveData(MethodAnalysis.ResponseType))
+            if (MethodAnalysis.ResponseType.ContainsSensitiveData())
             {
                 writer.WriteLine();
                 writer.WriteLine("protected override bool IsSensitiveResponse { get; set; } = true;");
@@ -255,35 +255,6 @@ private void WriteGeneratedCmdletFlag(IndentedTextWriter writer)
             writer.WriteLine("protected override bool IsGeneratedCmdlet { get; set; } = true;");
         }
 
-        /// <summary>
-        /// Checks if the type contains any sensitive data by going recursivly over all the internal properties
-        /// </summary>
-        private bool ContainsSensitiveData(Type type, Dictionary<Type, bool> visitedTypes = null)
-        {
-            if (visitedTypes == null) 
-                visitedTypes = new Dictionary<Type, bool>();
-
-            if (visitedTypes.ContainsKey(type)) 
-                return false;
-
-            visitedTypes.Add(type, true);
-
-            foreach (var childProperty in type.GetProperties())
-            {
-                if (IsSensitive(childProperty) || ContainsSensitiveData(childProperty.PropertyType, visitedTypes)) 
-                    return true;
-            }
-            return false;
-        }
-
-        private bool IsSensitive(PropertyInfo propertyInfo)
-        {
-            dynamic awsPropertyAttribute = propertyInfo.GetCustomAttributes()
-                .Where(attribute => attribute.GetType().FullName == "Amazon.Runtime.Internal.AWSPropertyAttribute").SingleOrDefault();
-
-            return awsPropertyAttribute != null && awsPropertyAttribute.Sensitive;
-        }
-
         private void WriteConverters(IndentedTextWriter writer, SimplePropertyInfo property, Param paramCustomization)
         {
             if (paramCustomization?.AutoConvert == Param.AutoConversion.ToBase64)