title: JPA ManyToMany unidirectional relationship
body: <p>Lets say we have two Entities, Entity <code>Node</code> and Entity <code>Cluster</code>.
  A <code>Cluster</code> has many <code>Node</code>s. A <code>Node</code> can belong to multiple <code>Cluster</code>. So in <code>Cluster</code> there is a <code>@ManyToMany</code> annotation. However <code>Node</code> is unaware of any <code>Cluster</code> it belongs to (intentional).</p>
  
  <p>When I delete a <code>Cluster</code> I want to keep all the <code>Node</code>s (in future I may add those <code>Node</code>s to another <code>Cluster</code>) it had. So I <strong>don't need</strong> <code>Cascade.DELETE</code>. But If I delete a <code>Node</code>,  all the <code>Cluster</code> it belonged to should be updated (the <code>Node</code> will be removed from them).</p>
  
  <p>What is the best way to handle this using JPA ? </p>