Pipe raw request data in a file
I can't seem to find how to actually pipe data sent from client into a file on the server.  
I don't want to use any third party plugin, I try to remain raw here if that's possible.

On the front I send blob data (audio) from the fetch function 

```javascript
const response = await fetch('/api/audio', {
  method: 'POST',
  body: this._blobData,
});
```

`_blobData` is just a `Blob` object. When it's sent it appears to be raw data representing an audio.

<img src="https://i.imgur.com/04JOSEw.png">

How can I pipe this on the server-side into a file ?

I tried to find a property in the context object that may hold/contain the data but I can't find.

Thanks in advance.