Getting "422 Unprocessable Entity" error when positing stringified body from node.js to Python FastAPI [duplicate]

I have this request, on my node.js application :

return new Promise((resolve, reject) => {      const options = {        hostname: 'py', <== docker container        port: 8000,        path: '/resume',        method: 'POST',        headers: {'Content-Type': 'application/json',        },        body: JSON.stringify({          file        })      }      const req = http.request(options, (res) => {        const body = [];        console.log('STATUS: '+ res.statusCode);        console.log('HEADERS: '+ JSON.stringify(res.headers));        res.setEncoding('utf8');        res.on('data', (chunk) => {          console.log('BODY: '+ chunk);          body.push(chunk);        });        resolve(body);      });      req.on('error', (error) =>{        console.log('problem with request: '+ error.message);        reject(error)      });      req.end();    })

And this, on my python app, that I copied from this topic => https://stackoverflow.com/a/65141532/14317753

@app.post("/resume")async def resume(request: Request):    da = await request.form()    da = jsonable_encoder(da)    print('file', da)    return da

But unfortunately, da is an empty string.

Obviously, I've tried everything : changing the GET request to POST and putting the get file param into a base64 file body param, using the request.json() and the request.body() instead of request.form() for the fixes I remember.

Thanks for you help.