endpoints: Surface failed event errors in logs

I wasn't able to make out what was wrong while running LCS, as the
unexpected error message wasn't much to go on with. Upon surfacing the
actual error, I noticed that the failed event fired since I had hit my
token limit, which I believe is useful enough information to be
surfaced.

I understand if this wasn't done earlier to prevent sensitive data
leakage, in which case, I'll close this, or add a case to surface only
when token limit is hit, although that may be tricky since different
LLMs report that in different ways.

Signed-off-by: Pranshu Srivastava <rexagod@gmail.com>

Author: rexagod

src/app/endpoints/streaming_query_v2.py

@@ -266,6 +266,7 @@ async def response_generator(  # pylint: disable=too-many-branches,too-many-stat
                 )
                 error_response = InternalServerErrorResponse.query_failed(error_message)
                 logger.error("Error while obtaining answer for user question")
+                logger.debug("Full error response: %s", failed_chunk.response)
                 yield format_stream_data(
                     {"event": "error", "data": {**error_response.detail.model_dump()}}
                 )