Add UnwrapXmlOutput Customization for GetBucketLocation (#3907)

Author: peterrsongg

generator/ServiceClientGeneratorLib/Customizations.cs

@@ -426,6 +426,7 @@ public class CustomizationsModel
         public const string OriginalMemberKey = "originalMember";
         public const string OverrideTreatEnumsAsStringKey = "overrideTreatEnumsAsString";
         public const string ExcludeMembersKey = "excludeMembers";
+        public const string UnwrapXmlOutputKey = "unwrapXmlOutput";
 
         JsonData _documentRoot;
 
@@ -596,6 +597,29 @@ public List<string> ExcludeMembers(string shapeName)
 
         }
 
+        /// <summary>
+        /// This customization is used to unwrap the response, and is only used for Xml services.
+        /// This is currently only used for GetBucketLocation
+        /// where the output is not wrapped in a top-level output xml tag and only includes the member at the root level
+        /// example usage:
+        /// "unwrapOutput:{
+        ///   "GetBucketLocationOutput": true
+        /// }
+        /// </summary>
+        /// <param name="shapeName">The shape to unwrap</param>
+        /// <returns></returns>
+        /// <exception cref="InvalidCastException"></exception>
+        public bool UnwrapXmlOutput(string shapeName)
+        {
+            var data = _documentRoot[UnwrapXmlOutputKey];
+            // if the customization doesn't exist, the default is false
+            if (data == null || data[shapeName] == null) return false;
+            if (!data[shapeName].IsBoolean)
+                throw new InvalidCastException("The value for the UnwrapOutput customization must be a boolean");
+
+            return (bool)data[shapeName];
+        }
+
         /// <summary>
         /// A list of uri properties for the service where we should not do validation for presence.
         /// </summary>