MapStream - remap tuple value(s)

Remap from (k,v) => k -> newKey -> value

e.g.  with

map(<stream>,"cand_id=add-distinct") , convert stream tuples from

From

{"cand_id":5718,id:123,v_i:345}

To

{
  id:123,
  v_i:345,
  "cand_id": {
    "add-distinct": 5718
}, 

Useful for update stream for atomic updates.