I am trying to invoke a REST endpoint with file upload and JSON data as below;

req : {JSON}
file: <File>

My JS is as below;

formData.append("req", JSON.stringify(data));
formData.append("file", file);

axios.post(url, formData, {
    headers: {
        "Content-Type": `multipart/form-data`
    }
})

However, I am getting 415 – Unsupported Media Type error

My Response header is as below;

accept: application/json,application/*+json 
content-type: application/json 
vary: Origin,Access-Control-Request-Method,Access-Control-Request-Headers,Accept-Encoding 

Not sure where the issue is.