SQL & PL/SQL

Hello,

I have a question that looks easy but I can't find a solution. I wonder if anyone could help?

If I have two different json objects. they can contain as many key, values as possible (or even nested json objects).

WITH json1 AS (
  SELECT JSON_OBJECT('key1' : 'val1') AS j FROM dual
), json2 AS (
  SELECT JSON_OBJECT('key2' : 'val2') AS j FROM dual
)
SELECT *
  from json1, json2;

is it possible to have a concatenation of both json objects easilly? If I take this simple exemple, I would like to have this:

{
 'key1', 'val1', 
 'key2', 'val2'
}

I'm using Oracle 19c.