Fix json_metadata for created posts

[singhpratyush]

Here is the desired format -

{
  "json_metadata": {
    "app": "hapramp/x.x.x",
    "format": "markdown",
    "tags": ["xxx", "yyy", "zzz"],
    "image": ["xxx", "yyy", "zzz"],
    "users": ["xxx", "yyy", "zzz"],
    "links": ["xxx", "yyy", "zzz"],
  }
}