.Net: Add Usage Metadata for ChatClientChatCompletionService Adapter (#12412)

### Motivation and Context

As part of Agents code-base is commong practice now to acquire `Usage`
from the ChatMessageContent.Metadata, although is different how this is
done with the new `Microsoft.Extensions.AI` relying on the
`UsageDetails` or `UsageContent` to avoid any disruption when migrating
`Agent`s to use the `IChatClient`. This change was made, so old code can
still function.

Co-authored-by: Mark Wallace <127216156+markwallace-microsoft@users.noreply.github.com>

Author: rogerbarreto

dotnet/src/InternalUtilities/samples/AgentUtilities/BaseAgentsTest.cs

@@ -9,8 +9,8 @@
 using Microsoft.SemanticKernel.ChatCompletion;
 using OpenAI.Assistants;
 using OpenAI.Files;
-
 using ChatTokenUsage = OpenAI.Chat.ChatTokenUsage;
+using UsageDetails = Microsoft.Extensions.AI.UsageDetails;
 
 /// <summary>
 /// Base class for samples that demonstrate the usage of host agents
@@ -125,6 +125,10 @@ protected void WriteAgentChatMessage(ChatMessageContent message)
             {
                 WriteUsage(chatUsage.TotalTokenCount, chatUsage.InputTokenCount, chatUsage.OutputTokenCount);
             }
+            else if (usage is UsageDetails usageDetails)
+            {
+                WriteUsage(usageDetails.TotalTokenCount ?? 0, usageDetails.InputTokenCount ?? 0, usageDetails.OutputTokenCount ?? 0);
+            }
         }
 
         string FormatAuthor() => message.AuthorName is not null ? $" - {message.AuthorName ?? " * "}" : string.Empty;

dotnet/src/SemanticKernel.Abstractions/AI/ChatClient/ChatMessageExtensions.cs

@@ -15,7 +15,7 @@ internal static ChatMessageContent ToChatMessageContent(this ChatMessage message
             ModelId = response?.ModelId,
             AuthorName = message.AuthorName,
             InnerContent = response?.RawRepresentation ?? message.RawRepresentation,
-            Metadata = message.AdditionalProperties,
+            Metadata = new AdditionalPropertiesDictionary(message.AdditionalProperties ?? []) { ["Usage"] = response?.Usage },
             Role = new AuthorRole(message.Role.Value),
         };
 

dotnet/src/SemanticKernel.Abstractions/AI/ChatClient/ChatResponseUpdateExtensions.cs

@@ -1,5 +1,6 @@
 // Copyright (c) Microsoft. All rights reserved.
 
+using System.Collections.Generic;
 using System.Text.Json;
 using Microsoft.SemanticKernel;
 using Microsoft.SemanticKernel.ChatCompletion;
@@ -34,9 +35,18 @@ item is Microsoft.Extensions.AI.FunctionCallContent fcc ?
 
             if (resultContent is not null)
             {
+                resultContent.InnerContent = item.RawRepresentation;
                 resultContent.ModelId = update.ModelId;
                 content.Items.Add(resultContent);
             }
+
+            if (item is Microsoft.Extensions.AI.UsageContent uc)
+            {
+                content.Metadata = new Dictionary<string, object?>(update.AdditionalProperties ?? [])
+                {
+                    ["Usage"] = uc
+                };
+            }
         }
 
         return content;