File upload works as documented, but SPA's also can upload file's via JSON in body#151

Would it be possible to support this other way of file upload? I now handle it with this code in my view: ``` data = request.get_json() image_mime, image_base64 = data["image_1"]["src"].split(",") image = base64.b64decode(image_base64) ``` Swagger specs are not in sync how this endpoint should be used. I ran into this by using React-Admin file upload which support Drag and drop fileupload: https://marmelab.com/react-admin/DataProviders.html#decorating-your-data-provider-example-of-file-upload