title: What is the default WindowBytesStoreSupplier for stream-stream join in Kafka Streams?
body: <p>The new API has a signature of:</p>
  
  <p><code>join(KStream&lt;K,VO&gt; otherStream, ValueJoiner&lt;? super V,? super VO,? extends VR&gt; joiner, JoinWindows windows, StreamJoined&lt;K,V,VO&gt; streamJoined)</code></p>
  
  <p>If I only set store name using <code>StreamJoined&lt;K,V,VO&gt; streamJoined</code> parameter, what would be the default configuration of <code>WindowBytesStoreSupplier</code> in terms of <code>retentionPeriod</code>, <code>windowSize</code> and <code>retainDuplicates</code>? It's not clear from documentation. Is this an in memory state store? Or default one configured by Kafka Streams?</p>