Add CBOR feature id and include it for operations called using CBOR protocol (#3933)

Author: muhammad-othman

sdk/src/Core/Amazon.Runtime/Internal/UserAgent/UserAgentFeatureId.cs

@@ -51,6 +51,11 @@ public class UserAgentFeatureId : ConstantClass
         /// </summary>
         public static readonly UserAgentFeatureId GZIP_REQUEST_COMPRESSION = new UserAgentFeatureId("L");
 
+        /// <summary>
+        /// An operation called using the Smithy RPC v2 CBOR protocol.
+        /// </summary>
+        public static readonly UserAgentFeatureId PROTOCOL_RPC_V2_CBOR = new UserAgentFeatureId("M");
+
         /// <summary>
         /// An operation called using a user provided endpoint URL.
         /// </summary>

sdk/src/Core/Amazon.Runtime/Pipeline/Handlers/Marshaller.cs

@@ -126,6 +126,12 @@ private static void SetRecursionDetectionHeader(IDictionary<string, string> head
 
         private static void UpdateUserAgentDetails(IRequestContext requestContext)
         {
+            if (requestContext.Request.Headers.TryGetValue("smithy-protocol", out var smithyProtocol)
+                && smithyProtocol == "rpc-v2-cbor")
+            {
+                requestContext.UserAgentDetails.AddFeature(UserAgentFeatureId.PROTOCOL_RPC_V2_CBOR);
+            }
+
             var accountIdMode = requestContext.ClientConfig.AccountIdEndpointMode;
             if (accountIdMode == AccountIdEndpointMode.DISABLED)
                 requestContext.UserAgentDetails.AddFeature(UserAgentFeatureId.ACCOUNT_ID_MODE_DISABLED);