title: convert content URI to FileUpload
body: <p>I get content URI from getContent and I want to convert it to FileUpload</p>
  <pre><code>  object upload : FileUpload(mimetype) {
      override fun contentLength(): Long {
        TODO(&quot;return contentLength here&quot;)
      }
      override fun fileName(): String? {
        TODO(&quot;return fileName to use in the multipart request here&quot;)
      }
      override fun writeTo(sink: BufferedSink) {
        TODO(&quot;write the data here&quot;)
      }
    }
  </code></pre>