A Kafka input plugin is getting messages in json format and being parsed by the json filter. One of the root keys -- transaction_details -- can contain a very large number of fields that we don't want to flatten into discreet fields. Would like to be able to convert the transaction_details root key from an object to a string that can be mapped as a text field and thus searchable as text but not selectable as a field in Kibana. We want to keep all the other json keys as they are when parsed. I can't seem to find a way (other than some kind of regular expression that seems very complicated and probably above my pay grade) to do this.
Sharing any thoughts would be most appreciated.