Update agent_service: support specify model

agent_service.py

@@ -300,7 +300,14 @@ class AgentService:
         if configs.get().get('debug_flags', {}).get('disable_llm_api_call', False):
             return 'LLM模拟回复 {}'.format(datetime.now().strftime("%Y-%m-%d %H:%M:%S"))
         if chat_service_type == ChatServiceType.OPENAI_COMPATIBLE:
-            if chat_config.get('use_multimodal_model', False):
+            # 指定了LLM模型则优先使用指定模型
+            if chat_config.get('model_name', None):
+                llm_client = chat_service.OpenAICompatible.create_client(chat_config['model_name'])
+                chat_completion = llm_client.chat.completions.create(
+                    messages=chat_config['messages'],
+                    model=chat_config['model_name'],
+                )
+            elif chat_config.get('use_multimodal_model', False):
                 chat_completion = self.multimodal_model_client.chat.completions.create(
                     messages=chat_config['messages'],
                     model=self.multimodal_model_name,