Truncate online query to Serper if query exceeds max supported length

Previously query to serper with longer than max supported would throw
error instead of returning at least some results.

Truncating the onlien search query to serper to max supported length
mitigates that issue.

Author: debanjum

src/khoj/processor/tools/online_search.py

@@ -327,9 +327,16 @@ async def search_with_google(query: str, location: LocationData) -> Tuple[str, D
 
 
 async def search_with_serper(query: str, location: LocationData) -> Tuple[str, Dict[str, List[Dict]]]:
+    headers = {"X-API-KEY": SERPER_DEV_API_KEY, "Content-Type": "application/json"}
     country_code = location.country_code.lower() if location and location.country_code else "us"
+    max_query_length = 2048
+    if len(query) > max_query_length:
+        logger.warning(
+            f"Truncate online query. Query length {len(query)} exceeds {max_query_length} supported by Serper. Query: {query}"
+        )
+        query = query[:max_query_length]
+
     payload = json.dumps({"q": query, "gl": country_code})
-    headers = {"X-API-KEY": SERPER_DEV_API_KEY, "Content-Type": "application/json"}
 
     async with aiohttp.ClientSession() as session:
         async with session.post(SERPER_DEV_URL, headers=headers, data=payload) as response: