title: Splitting JDL file to extend model step by step
body: <p>A freshly generated JHipster application contains already a basic model (e.g. with an User entity), lets call it m0.
  I extended m0 by defining a model m1 with the JHipster Domain Language (JDL) and generating the entities.
  For the authorization layer m1 had to reference the User in m0. I was able to achieve that by defining the User entity in the m1.jdl file like this:</p>
  
  <pre><code>entity User{}
  </code></pre>
  
  <p>The already existing User entity was not regenerated, only referenced from m1 - great!</p>
  
  <p>Since m1 has to be extended with new entities regularly, it would be a dream to use the same pattern for m2, m3 referencing an entity in m1. But when I define AnM1Entity in m2.jdl like this:</p>
  
  <pre><code>entity AnM1Entity{}
  </code></pre>
  
  <p>Unfortunately AnM1Entity{} is regenerated and all attributes defined in m1.jdl for AnM1Entity are lost.</p>
  
  <p>Why is User not regnerated and AnM1Entity is regenerated? Is there a way to skip the generation of AnM1Entity?</p>
  
  <p>Or is there another way to extend JHipster application models in a convenient way?</p>
  
  <p>thanks</p>