Is a JSON string valid to be used in attachment data json?

[TimoGlastra]

When using attachments with the json keyword, it is expected that the value is JSON.

JSON also sees an ecoded string (e.g. "Timo") as valid JSON, so are these also allowed as the value for JSON attachments, or are only JSON arrays and JSON objects allowed and should the base64 encoding be used in this case (there's no need to re-encode really, we already have a base type of JSON).

See https://developer.mozilla.org/en-US/docs/Learn/JavaScript/Objects/JSON#other_notes for note that any json value is valid JSON in itself