Message in JSON logs is not stringified

What's going wrong?

JSON logs dont support JSON data

How could we reproduce this issue?

Run any PM2 app with --json and console out an object. For example:

console.error({this: 'foo'})

Actual err log

{
  "message":"{\n  this: 'foo'\n}",
  "timestamp":"2021-12-08T22:20:27",
  "type":"err",
  "process_id":0,
  "app_name":"Log test ap"
}

Expected err log

{
  "message":"{\"this\": \"foo\"}",
  "timestamp":"2021-12-08T22:20:27",
  "type":"err",
  "process_id":0,
  "app_name":"Log test ap"
}

Note: I formatted the above json objects to make them easier to read here. I would expect to see them all on one line as they are currently in my logs

EDIT:
I also noticed that the strout logs seem to be fine

out_file example

{
  "message":"{\"level\":20,\"msg\":\"POST /test/endpoint (242 ms) 200\",\"pid\":16016,\"hostname\":\"ip-123-12-12-123\",\"v\":1}\n",
  "timestamp":"2021-12-10T01:14:05.145Z",
  "type":"out",
  "process_id":0,
  "app_name":"Jobs Marketplace Log test ap"
}

Start by running any PM2 app with --json and console.error({this: 'foo'}), then compare the err and out log formats shown in the issue. The issue names no files or tests; done means err JSON logs encode the object as JSON in the message, preserve the surrounding fields, and remain on one line.