Stop Re-Stringifing Strings

[benonymity]

I spent a great deal of time debugging why

response = await HTTP.post(apiUrl, {
    body: JSON.stringify(requestPayload),
    headers: {
        'Content-Type': 'application/json'
    }
});

was sending a malformed body. I eventually removed JSON.stringify() from my payload and the request worked. Turns out there is no check for whether the body is a string or an object, so all strings are re-stringified, which messes up the body. This just adds a simple check to only stringifies non-bodies.