title: Camel aggregator complete aggregation on new correlation key
body: <p>Basically I have a group of large strings that are sent to the aggregator in smaller chunks. I would like to aggregate them back into the full strings.</p>
  
  <p>the header has an strId, I would like to use it as a correlation key. The aggregation for previous string should be complete when we receive a header with new strId. </p>
  
  <p>I would like to know if this is possible with camel aggregator</p>