Rename and enhance ChatService methods

Renamed `CreateQuestionAsync` to `CreateReformulateQuestionAsync` for clearer intent. Updated `CreateChatAsync` to include a new `ChatSystemPrompt` property in `AzureOpenAIPromptExecutionSettings` and modified `ChatHistory` initialization to simplify setup. Removed redundant `prompt` string construction and added user messages directly to `ChatHistory`.

Updated `VectorSearchService` to use the renamed `CreateReformulateQuestionAsync` method for consistency. These changes improve code clarity, maintainability, and functionality.

SqlDatabaseVectorSearch/Services/ChatService.cs

@@ -86,7 +86,7 @@ public class ChatService(IChatCompletionService chatCompletionService, Tokenizer
         Remember to ALWAYS end your answer with a period followed by a space before adding citations.
         """;
 
-    public async Task<ChatResponse> CreateQuestionAsync(Guid conversationId, string question, CancellationToken cancellationToken = default)
+    public async Task<ChatResponse> CreateReformulateQuestionAsync(Guid conversationId, string question, CancellationToken cancellationToken = default)
     {
         var chat = await GetChatHistoryAsync(conversationId, cancellationToken);
 
@@ -170,11 +170,10 @@ public class ChatService(IChatCompletionService chatCompletionService, Tokenizer
     {
         var settings = new AzureOpenAIPromptExecutionSettings
         {
-            MaxTokens = appSettings.MaxOutputTokens
+            MaxTokens = appSettings.MaxOutputTokens,
+            ChatSystemPrompt = systemPromptForAnswering
         };
 
-        var chat = new ChatHistory(systemPromptForAnswering);
-
         var prompt = new StringBuilder($"""
             Answer the following question:
             ---
@@ -210,6 +209,7 @@ public class ChatService(IChatCompletionService chatCompletionService, Tokenizer
             }
         }
 
+        var chat = new ChatHistory();
         chat.AddUserMessage(prompt.ToString());
 
         return (chat, settings);

SqlDatabaseVectorSearch/Services/VectorSearchService.cs

@@ -143,7 +143,7 @@ public partial class VectorSearchService(IServiceProvider serviceProvider, Appli
     private async Task<(ChatResponse ReformulatedQuestion, int EmbeddingTokenCount, IEnumerable<Entities.DocumentChunk> Chunks)> CreateContextAsync(Question question, bool reformulate, CancellationToken cancellationToken)
     {
         // Reformulate the question taking into account the context of the chat to perform keyword search and embeddings.
-        var reformulatedQuestion = reformulate ? await chatService.CreateQuestionAsync(question.ConversationId, question.Text, cancellationToken) : new(question.Text);
+        var reformulatedQuestion = reformulate ? await chatService.CreateReformulateQuestionAsync(question.ConversationId, question.Text, cancellationToken) : new(question.Text);
 
         var embeddingTokenCount = tokenizerService.CountEmbeddingTokens(reformulatedQuestion.Text!);
         logger.LogDebug("Embedding Token Count: {EmbeddingTokenCount}", embeddingTokenCount);