Rider HTTP Client Build JWT Token in Pre-Reques Script

Question

Currently using Rider HTTP Client Plugin as documented here to build out some API test scripts and sample calls. For one of the tests I need to build a JWT token in the Pre-Rquest Script and after many failed attempts I post this question.

this is my current script, have tried a few diff variations with no luck.

    let header = JSON.stringify({"alg": "HS512"});
    let body = JSON.stringify({
        "username": request.environment.get('the_big_username'),
        "entity": request.environment.get('the_big_entity'),
        "datetime": new Date().toISOString()
    });
    
    let theBigSecret = request.environment.get("the_big_secret");
    let theHeader = crypto.sha512()
        .updateWithText(header)
        .digest()
        .toBase64(true)
    
    let theBody = crypto.sha512()
        .updateWithText(body)
        .digest()
        .toBase64(true)
    
    const content = `${theHeader}.${theBody}`
    let theSignature = encodeURIComponent(crypto.hmac.sha512()
        .withTextSecret(theBigSecret)
        .updateWithText(content)
        .digest()
        .toBase64(true))

    
    const allTogetherNow = `${content}.${theSignature}`

    // pm.globals.set('jws', signedJws);
    request.variables.set('the_big_token', allTogetherNow);

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so far all results fail and are not decodable by jwt.io and after much searching and documentation reading I have not gotten any closer to understanding where I am going wrong.

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