title: How to query models by a property that is an array
body: <p>I'm trying to do a 'findOne' operation in a model that has an array property and filter the results to only list the item if the string im searching is in that array.</p>
  
  <p>Example:</p>
  
  <pre><code>  var AppUser = server.loopback.getModel('AppUser');
    AppUser.create({
      "name":"juan"
      "favoriteLetters":["a","b","c"]
    },function(){
      AppUser.findOne({where:{favoriteLetters:'a'}},function(error,appUser){
        console.log(error,appUser);
      });
    });
  </code></pre>
  
  <p>So in this case i want to find a 'appUser' that has a favorite letter 'a'.</p>
  
  <p>Thanks.</p>