title: What changes can I make to a cloud-endpoint (app-engine) return object before I need a new API version? (and how is that done)
body: <p>I have an App-Engine service endpoint that is returning a POJO object consisting of many fields of various types.  The Android client, built with the corresponding endpoint-libs, accepts this just fine.</p>
  
  <p>If I <em>add</em> new fields to the <em>end</em> of this object definition and start returning that extended object from the App-Engine servers, will older Android clients accept this and just ignore the extra, or will they barf?</p>
  
  <p>I see mention of support of different "versions" of an API, which seems to be required if I can't extend my return object, but information on <em>how</em> to write this is difficult to find.  Any pointers?</p>
  
  <p>Or, perhaps <strong>more simply...</strong>  What is the best way to return different information to a REST call than previous server versions and still be backward compatible with older clients?  Something like <a href="https://code.google.com/p/objectify-appengine/" rel="nofollow">Objectify</a>-for-Endpoints would be perfect.</p>