Grafana with x-ndjson


I want to query Elasticsearch index from Grafana with multisearch using the bulk API with the newline delimited JSON (NDJSON) format. like this

curl -u myuser -i -H “Content-Type: application/json” -XPOST "http://host_ES:900/index/_msearch --data-binary ’
{ xxxx}

The query work well either we made json or x-ndjson,

However when we query through Knox gateway, it gives
HTTP/1.1 400 Bad Request
content-type: application/json

But when we replace json by x-ndjson like mentioned in the bulk API, it work well.

My question is how to force Grafana to POST data with ‘content-type: application/x-ndjson’ to be able query ES via Knox, because the new delimited newline doesn’t work via Knox using application/json