Allow configuring OpenAI chat model for Khoj chat

- Simplifies switching between different OpenAI chat models. E.g GPT4
- It was previously hard-coded to use gpt-3.5-turbo. Now it just
  defaults to using gpt-3.5-turbo, unless chat-model field under
  conversation processor updated in khoj.yml

src/khoj/processor/conversation/gpt.py

@@ -236,12 +236,11 @@ A:{ "search-type": "notes" }"""
     return json.loads(story.strip(empty_escape_sequences))
 
 
-def converse(references, user_query, conversation_log={}, api_key=None, temperature=0.2):
+def converse(references, user_query, conversation_log={}, model="gpt-3.5-turbo", api_key=None, temperature=0.2):
     """
     Converse with user using OpenAI's ChatGPT
     """
     # Initialize Variables
-    model = "gpt-3.5-turbo"
     compiled_references = "\n\n".join({f"# {item}" for item in references})
 
     personality_primer = "You are Khoj, a friendly, smart and helpful personal assistant."

src/khoj/routers/api.py

@@ -208,6 +208,7 @@ def chat(q: Optional[str] = None):
     # Initialize Variables
     api_key = state.processor_config.conversation.openai_api_key
     model = state.processor_config.conversation.model
+    chat_model = state.processor_config.conversation.chat_model
     user_message_time = datetime.now().strftime("%Y-%m-%d %H:%M:%S")
 
     # Load Conversation History
@@ -234,7 +235,7 @@ def chat(q: Optional[str] = None):
 
     try:
         with timer("Generating chat response took", logger):
-            gpt_response = converse(compiled_references, q, meta_log, api_key=api_key)
+            gpt_response = converse(compiled_references, q, meta_log, model=chat_model, api_key=api_key)
         status = "ok"
     except Exception as e:
         gpt_response = str(e)

src/khoj/utils/config.py

@@ -69,6 +69,7 @@ class ConversationProcessorConfigModel:
     def __init__(self, processor_config: ConversationProcessorConfig):
         self.openai_api_key = processor_config.openai_api_key
         self.model = processor_config.model
+        self.chat_model = processor_config.chat_model
         self.conversation_logfile = Path(processor_config.conversation_logfile)
         self.chat_session = ""
         self.meta_log: dict = {}

src/khoj/utils/rawconfig.py

@@ -82,6 +82,7 @@ class ConversationProcessorConfig(ConfigBase):
     openai_api_key: str
     conversation_logfile: Path
     model: Optional[str] = "text-davinci-003"
+    chat_model: Optional[str] = "gpt-3.5-turbo"
 
 
 class ProcessorConfig(ConfigBase):