[fix] Convert NaNs and Infs in responses to strings

[n-gao]

This PR introduces a recursive function that replaces all np.nan by NaN, np.inf by inf and -np.inf by -inf as strings to avoid JSON encoding errors. An alternative would be to use the orjson but then these instances would be replaced by None.

[mihran113]

Hey @n-gao! Thanks a lot for contribution.
My concern is the efficiency here, as for larger run params, this might take a while actually.
My suggestion is to do something like this:

    response_string = json.dumps(
            response,
            ensure_ascii=False,
            allow_nan=True,
            indent=None,
            separators=(",", ":"),
        )
    parsed_response_string = re.sub(r'(NaN|Infinity|-Infinity)', r'"\1"', response_string)
    return Response(parsed_response_string.encode('utf-8'), media_type="application/json")

As Fastapi's JSONResponse dumps the dict into a string anyways, so we can do that step manually, and add quotes around the values that are not json encodable, I guess this will do the trick much more efficiently.
What do you think about this approach?

[n-gao]

Hi @mihran113, thanks for the feedback! I wouldn't fear much about the performance of the metric as it is very similar to the python JSON encoder. So, using json.dumps will roughly have the same runtime. So, first replacing NaNs and then encoding will have at most double the runtime then first encoding and then replacing. If one accounts for the extra time to search through the whole string to replace substrings, the runtimes are probably going to be very close. But, the main reason I'd avoid such an implementation is that if any string contains the word NaN, Infinity, or -Infinity this approach would break the string.

[mihran113]

yeah, makes sense, and after all this will be a temporary fix, before we move this endpoint to streaming response as well. So, can I ask you to update changelog as well, so I can merge the PR?

Here's an example how to do it, as there's no other changes yet after the patches:

## Unreleased 

### fixes
-  Convert NaNs and Infs in responses to strings (n-gao)

[n-gao]

done! :)

[mihran113]

oh, seems there was just a change on changelog, sorry about that, but there's a conflict now

[n-gao]

resolved

[mihran113]

Great work! Thanks for the contribution.

[mihran113]

Resolves #2629