Throw an error when quickwit is responding a status_code >= 400

[idrissneumann]

Today with the #23 PR, we got this piece of code to improve the debugging:

if res.StatusCode >= 400 {
		jsonResponseBody, _ := json.Marshal(res.Body)
		jsonQueryParam, _ := json.Marshal(queryParams)
		jsonRequestBody, _ := json.Marshal(r.Requests)
		c.logger.Error("Error on multisearch: statusCode = " + strconv.Itoa(res.StatusCode) + ", responseBody = " + string(jsonResponseBody) + ", queryParam = " + string(jsonQueryParam) + ", requestBody = " + string(jsonRequestBody))
	}

Improve this by throwing directly an error, you'll probably have to fix some unit tests.

[idrissneumann]

It's a duplicate of #28