add prompt to message (#2099)

### What problem does this PR solve?

#2098

### Type of change
 
- [x] New Feature (non-breaking change which adds functionality)

api/apps/conversation_app.py

             if not conv.reference:
                 conv.reference.append(ans["reference"])
             else: conv.reference[-1] = ans["reference"]
-            conv.message[-1] = {"role": "assistant", "content": ans["answer"], "id": message_id}
+            conv.message[-1] = {"role": "assistant", "content": ans["answer"],
+                                "id": message_id, "prompt": ans.get("prompt", "")}
 
         def stream():
             nonlocal dia, msg, req, conv

api/db/services/dialog_service.py

                 for m in messages if m["role"] != "system"])
     used_token_count, msg = message_fit_in(msg, int(max_tokens * 0.97))
     assert len(msg) >= 2, f"message_fit_in has bug: {msg}"
+    prompt = msg[0]["content"]
 
     if "max_tokens" in gen_conf:
         gen_conf["max_tokens"] = min(
             max_tokens - used_token_count)
 
     def decorate_answer(answer):
-        nonlocal prompt_config, knowledges, kwargs, kbinfos
+        nonlocal prompt_config, knowledges, kwargs, kbinfos, prompt
         refs = []
         if knowledges and (prompt_config.get("quote", True) and kwargs.get("quote", True)):
             answer, idx = retr.insert_citations(answer,
 
         if answer.lower().find("invalid key") >= 0 or answer.lower().find("invalid api") >= 0:
             answer += " Please set LLM API-Key in 'User Setting -> Model Providers -> API-Key'"
-        return {"answer": answer, "reference": refs}
+        return {"answer": answer, "reference": refs, "prompt": prompt}
 
     if stream:
         answer = ""
-        for ans in chat_mdl.chat_streamly(msg[0]["content"], msg[1:], gen_conf):
+        for ans in chat_mdl.chat_streamly(prompt, msg[1:], gen_conf):
             answer = ans
-            yield {"answer": answer, "reference": {}}
+            yield {"answer": answer, "reference": {}, "prompt": prompt}
         yield decorate_answer(answer)
     else:
-        answer = chat_mdl.chat(
-            msg[0]["content"], msg[1:], gen_conf)
+        answer = chat_mdl.chat(prompt, msg[1:], gen_conf)
         chat_logger.info("User: {}|Assistant: {}".format(
             msg[-1]["content"], answer))
         yield decorate_answer(answer)
         chat_logger.warning("SQL missing field: " + sql)
         return {
             "answer": "\n".join([clmns, line, rows]),
-            "reference": {"chunks": [], "doc_aggs": []}
+            "reference": {"chunks": [], "doc_aggs": []},
+            "prompt": sys_prompt
         }
 
     docid_idx = list(docid_idx)[0]
         "answer": "\n".join([clmns, line, rows]),
         "reference": {"chunks": [{"doc_id": r[docid_idx], "docnm_kwd": r[docnm_idx]} for r in tbl["rows"]],
                       "doc_aggs": [{"doc_id": did, "doc_name": d["doc_name"], "count": d["count"]} for did, d in
-                                   doc_aggs.items()]}
+                                   doc_aggs.items()]},
+        "prompt": sys_prompt
     }