Instead of using image-uploader, which relies on the old UploadMixin, we can now use the uppy-image-uploader which uses the new UppyUploadMixin which is stable enough and supports both regular XHR uploads and direct S3 uploads, controlled by a site setting (default to XHR).
At some point it may make sense to rename uppy-image-uploader back to image-uploader, once we have gone through plugins etc. and given a bit of deprecation time period.
This commit also introduces
queryParams to lib/url.js,
which is a drop-in replacement for $.param to generate a
queryString from a JS object literal. A later PR will make
changes to more places in core and plugins to use this.