Currently, when using the text_similarity_reranker retriever, if something goes wrong during the rerank process, whether this is a direct error from the reranking service or issues due to changes in response etc, we propagate this exception all the way up and return a 4xx response to the user.

We could introduce a new parameter as part of the text_similarity_reranker retriever (defaults to false) which would allow "lenient reranking", i.e. give the option to return the results non reranked if something goes wrong during the rerank process.

We need to also take into account logging (as we don't want to pollute our logs with thousands of identical error logs) and how to actually notify the user that the results are not actually reranked.