title: InMemoryUploadedFile to binary string in Django
body: <p>I need to send file as BinaryData string to some API. Example</p>
  
  <pre><code>files = request.FILES
  for file in files.values():
      requests.post(
          url='some_url',
          headers={
              "Content-Type": "application/json",
              "Authorization": "Bearer {}".format(token)
          },
          json={
              "inputs": [
                  {
                      "type": "identity_assurance.document_verification.americas.us.drivers_license.image.back",
                      "value": {
                          "$objectType": "BinaryData",
                          "data": file.read(),
                          "metadata": {
                              "cropped": False
                          },
                          "mime_type": "image/png"
                      }
                  },
              ]
          }
      )
  </code></pre>
  
  <p>But I got <code>TypeError: Object of type bytes is not JSON serializable</code> on file.read(). In <code>data</code> field should be byte string</p>