Option to leave omitted columns in INSERT JSON unset

CASSANDRA-7304 introduced the ability to distinguish between NULL and UNSET prepared statement parameters.

When inserting JSON objects it is not possible to profit from this as a prepared statement only has one parameter that is bound to the JSON object as a whole. There is no way to control NULL vs UNSET behavior for columns omitted from the JSON object.

Please extend on CASSANDRA-7304 to include JSON support.

(My personal requirement is to be able to insert JSON objects with optional fields without incurring the overhead of creating a tombstone of every column not covered by the JSON object upon initial insert.)