revert: use blank User-Agent header when communicating with open-ai compatible service

This reverts commit 26ab0a7.

Signed-off-by: leo <longshuang@msn.cn>

Author: love-linger

src/AI/Service.cs

@@ -57,7 +57,12 @@ public string Model
 
         public async Task<List<string>> FetchAvailableModelsAsync()
         {
-            var allModels = GetOpenAIClient().GetOpenAIModelClient().GetModels();
+            var credential = new ApiKeyCredential(ReadApiKeyFromEnv ? Environment.GetEnvironmentVariable(ApiKey) : ApiKey);
+            var client = Server.Contains("openai.azure.com/", StringComparison.Ordinal)
+                ? new AzureOpenAIClient(new Uri(Server), credential)
+                : new OpenAIClient(credential, new() { Endpoint = new Uri(Server) });
+
+            var allModels = client.GetOpenAIModelClient().GetModels();
             AvailableModels = new List<string>();
             foreach (var model in allModels.Value)
                 AvailableModels.Add(model.Id);
@@ -77,15 +82,15 @@ public async Task<List<string>> FetchAvailableModelsAsync()
 
         public ChatClient GetChatClient()
         {
-            return !string.IsNullOrEmpty(Model) ? GetOpenAIClient().GetChatClient(Model) : null;
-        }
+            if (string.IsNullOrEmpty(Model))
+                return null;
 
-        private OpenAIClient GetOpenAIClient()
-        {
             var credential = new ApiKeyCredential(ReadApiKeyFromEnv ? Environment.GetEnvironmentVariable(ApiKey) : ApiKey);
-            return Server.Contains("openai.azure.com/", StringComparison.Ordinal)
-                ? new AzureOpenAIClient(new Uri(Server), credential, new AzureOpenAIClientOptions() { UserAgentApplicationId = string.Empty })
-                : new OpenAIClient(credential, new() { Endpoint = new Uri(Server), UserAgentApplicationId = string.Empty });
+            var client = Server.Contains("openai.azure.com/", StringComparison.Ordinal)
+                ? new AzureOpenAIClient(new Uri(Server), credential)
+                : new OpenAIClient(credential, new() { Endpoint = new Uri(Server) });
+
+            return client.GetChatClient(Model);
         }
 
         private string _name = string.Empty;