Json.pretty puts extensions in wrong place

[joeljons]

Json.pretty(openAPI) makes the extensions go under its own extension node. This results that when parsing it again they will be gone.

The variable prettyJson in my testcase has the value

{
  "openapi" : "3.0.0",
  "servers" : [ {
    "url" : "/"
  } ],
  "extensions" : {
    "x-some-extension" : "some-value"
  }
}

I would expect x-some-extensions to be directly under the root as it was in the initial json variable.