title: flink assign uid to window function
body: <p>is there a way to assign uid to a window function (such as apply(ApplyCustomFunction)) as we do for map/flatmap (or other) functions in Flink. The Flink version is 1.13.1.</p>
  <p>I would like to specify the case with an example</p>
  <pre><code>DataStream&lt;RECORD&gt; outputDataStream = dataStream
                  .coGroup(otherDataStream)
                  .where(DATA::getKey)
                  .equalTo(OTHERDATA::getKey)
                  .window(TumblingProcessingTimeWindows.of(Time.seconds(2)))
                  .apply(new CoGroupFunction());
  </code></pre>
  <p>Thanks</p>