Add ChatClientWithSystemMessage abstraction and extensions

Introduced the Volo.Abp.AI.Abstractions project with a new ChatClientWithSystemMessage delegate and related extension methods. Updated the solution and AbpAIModule to include and reference the new abstractions, supporting enhanced AI chat client extensibility.

framework/src/Volo.Abp.AI.Abstractions/Volo/Abp/AI/Delegates/ChatClientWithSystemMessage.cs

@@ -0,0 +1,52 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.Extensions.AI;
+
+namespace Volo.Abp.AI.Delegates;
+
+public class ChatClientWithSystemMessage : DelegatingChatClient
+{
+    public string SystemMessage { get; private set; }
+
+    public ChatClientWithSystemMessage(IChatClient innerClient, string systemMessage) : base(innerClient)
+    {
+        SystemMessage = systemMessage;
+    }
+
+    public override Task<ChatResponse> GetResponseAsync(IEnumerable<ChatMessage> messages, ChatOptions? options = null, CancellationToken cancellationToken = default)
+    {
+        return base.GetResponseAsync(PrepareMessages(messages), options, cancellationToken);
+    }
+
+    public override IAsyncEnumerable<ChatResponseUpdate> GetStreamingResponseAsync(IEnumerable<ChatMessage> messages, ChatOptions? options = null, CancellationToken cancellationToken = default)
+    {
+        return base.GetStreamingResponseAsync(PrepareMessages(messages), options, cancellationToken);
+    }
+
+    protected virtual List<ChatMessage> PrepareMessages(IEnumerable<ChatMessage> messages)
+    {
+        var messagesList = messages.ToList();
+
+        if(messagesList.Any(x => x.Role == ChatRole.System))
+        {
+            // If there is a system message, skip it. It might be continued conversation.
+            // No need to add a new one to prevent duplication.
+
+            // If developer provided system message, then it's overridden, still skipping.
+
+            // Logger.LogWarning("System message is not supported in ChatClientWithSystemMessage. Skipping.");
+
+            return messagesList;
+        }
+
+        if(!SystemMessage.IsNullOrEmpty())
+        {
+            messagesList.Insert(0, new ChatMessage(ChatRole.System, SystemMessage));
+        }
+
+        return messagesList;
+    }
+}

framework/src/Volo.Abp.AI/Volo/Abp/AI/AbpAIModule.cs

@@ -5,6 +5,9 @@ using Volo.Abp.Modularity;
 
 namespace Volo.Abp.AI;
 
+[DependsOn(
+    typeof(AbpAIAbstractionsModule)
+)]
 public class AbpAIModule : AbpModule
 {
     public override void PostConfigureServices(ServiceConfigurationContext context)

framework/src/Volo.Abp.AI/Volo/Abp/AI/Extensions/ChatClientWithSystemMessageExtensions.cs

@@ -0,0 +1,16 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using Microsoft.Extensions.AI;
+using Volo.Abp.AI.Delegates;
+
+namespace Volo.Abp.AI.Extensions;
+
+public static class ChatClientWithSystemMessageExtensions
+{
+    public static ChatClientBuilder UseSystemMessage(this ChatClientBuilder builder, string systemMessage)
+    {
+        return builder.Use(client => new ChatClientWithSystemMessage(client, systemMessage));
+    }
+}