Merge multiple audio files into one

curl --request POST \
  --url https://convertly.sh/api/media/concat-audio \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: multipart/form-data' \
  --form 'file=<string>' \
  --form file.items='@example-file'

const form = new FormData();
form.append('file', '<string>');
form.append('file.items', '{
  "fileName": "example-file"
}');

const options = {method: 'POST', headers: {Authorization: 'Bearer <token>'}};

options.body = form;

fetch('https://convertly.sh/api/media/concat-audio', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

{
  "files": [
    {
      "filename": "<string>",
      "mimeType": "<string>",
      "originalSize": 123,
      "finalSize": 123,
      "downloadUrl": "<string>"
    }
  ]
}

{
  "error": "<string>",
  "upgradeUrl": "<string>"
}

{
  "error": "<string>",
  "upgradeUrl": "<string>"
}

{
  "error": "<string>",
  "upgradeUrl": "<string>"
}

{
  "error": "<string>",
  "upgradeUrl": "<string>"
}

{
  "error": "<string>",
  "upgradeUrl": "<string>"
}

{
  "error": "<string>",
  "upgradeUrl": "<string>"
}