title: Use user login as default credential with Apache Zeppelin
body: <p>With Apache Zeppelin 0.7.2, I have setup LDAP authentication and would like to "forward" the user login to JDBC (a Spark thrift server) instead of the default "hive".</p>
  
  <p>I see Zeppelin has something called "credentials", but that means all users must fill it with any value :/</p>
  
  <p>I am going to automatically generate this file (<code>credentials.json</code>) with all users, or maybe there is a better solution?</p>