title: Mongoose enum Validation on String Arrays?
body: <p>Is it possible to use <code>enum</code> validation on <code>type: [String]</code>?</p>
  
  <p>Example:</p>
  
  <pre><code>var permitted = ['1','2','3'];
  
  var exampleSchema = new Schema({
      factors: {
              type: [String],
              enum: permitted,
              required: "Please specify at least one factor."
      }
  });
  </code></pre>
  
  <p>I would have expected that <code>factors</code> would only be able to contain the values in <code>permitted</code>.</p>