title: Camel exchange giving empty attachments for multipart request
body: <p>I am sending a multipart/form-data request (txt file) through postman to a camel rest endpoint.
  While inspecting the exchange object the attachmenstMap is coming up as null</p>
  
  <p>Camel Context:</p>
  
  <pre><code>&lt;camelContext id="batch2" xmlns="http://camel.apache.org/schema/spring"&gt;
  &lt;!-- List of Beans which extend RouteBuilder class--&gt;
  &lt;routeBuilder ref="miscRoute"/&gt;
  &lt;routeBuilder ref="batchRoute"/&gt;
  
  &lt;!-- REST Configuration --&gt;
  &lt;!-- Make sure your contextPath here matches web.xml --&gt;
  &lt;restConfiguration component="servlet" bindingMode="json" contextPath="rest" port="8080" enableCORS="true"&gt;
    &lt;dataFormatProperty key="prettyPrint" value="true"/&gt;
  &lt;/restConfiguration&gt;
  
  &lt;/camelContext&gt;
  </code></pre>
  
  <p>BatchRoute extends AbstractRouteBuilder :</p>
  
  <pre><code>@Override
  public void configure() {
  
      super.configure();
  
      rest("/batch")
      .id("createBatch").tag("createBatch")
      .produces(MediaType.APPLICATION_JSON)
      .consumes(MediaType.MULTIPART_FORM_DATA)
      .description("Create Batch")
      .post()
      .bindingMode(RestBindingMode.off)
      .param()
          .name(ApiParameter.BATCH_FILE.toString())
          .type(RestParamType.formData)
          .description(ApiParameter.BATCH_FILE.getDescription())
          .dataType(ApiParameter.BATCH_FILE.getType())
          .endParam()
      .outType(CreateBatchResponse.class)
      .route().removeHeader(Exchange.HTTP_PATH)
      .streamCaching("false")
      .process(new CreateBatchRequestProcessor())
      .process(exchange -&gt; {
          Map&lt;String, DataHandler&gt; attachmentsMap = exchange.getIn().getAttachments();
  
      })
      .to(ENDPOINT_REQUEST_BATCH2_CREATE_BATCH)
      .endRest();
  </code></pre>
  
  <p>AbstractRouteBuilder extends RouteBuilder:</p>
  
  <pre><code>@Override
  public void configure() {
  
      restConfiguration()
      .component("servlet")
      .port("8080")
      .contextPath("rest")
      .endpointProperty("attachmentMultipartBinding", "true");
  </code></pre>
  
  <p>Please suggest as how can we extract the attachment from exchange object.
  Thanks.</p>