I'm trying to set up GAS to send an API call to my CRM. Here is the link for the API documentation.

I'm attempting to use the code for sending a text via the API. Below is what they provided. I have changed this code to work with GAS(see further down):

var myHeaders = new Headers();
myHeaders.append("Content-Type", "application/json");
myHeaders.append("Authorization", "Bearer {{api_token}}");

var raw = JSON.stringify({
  "message": ""
});

var requestOptions = {
  method: 'PUT',
  headers: myHeaders,
  body: raw,
  redirect: 'follow'
};

fetch("https://api.kvcore.com/v2/public/contact/{{contact_id}}/text", requestOptions)
  .then(response => response.text())
  .then(result => console.log(result))
  .catch(error => console.log('error', error));

I adapted the code provided to work with GAS. This is what I'm actually trying to run:

function kvCoreStyle(){
  var myHeaders = {
   "Content-Type":"application/json",
   "Authorization":"Bearer {{TOKENID}}"
}

  var raw = {
      "message":"let me know if you get this text"
   }

  var requestOptions = {
   "method":"PUT",
   "headers":myHeaders,
   "body": raw,
   "redirect":"follow"
};
 
  UrlFetchApp.fetch("https://api.kvcore.com/v2/public/contact/{{ContactID}}/text", requestOptions)
    .then(response => response.text())
    .then(result => console.log(result))
    .catch(error => console.log('error', error));
}

Unfortunately, I keep getting an error saying "Request body must be a valid JSON string"

I have tried using JSON.stringify() on multiple portions of this and can not get it to work at all. Any advice would be appreciated!