title: Mongoose - find all documents whose array property contains a given subset?
body: <p>I have a (simplified) model based on the following schema:</p>
  
  <pre><code>schema = mongoose.Schema({
      foo: { type: String },
      bars: [{ type: String }]
  });
  model = mongoose.model ('model', schema);
  </code></pre>
  
  <p>and I want to create an API to return all documents that contain all of the 'bars' which are provided in a comma separated list.  So I have:</p>
  
  <pre><code>exports.findByBars = function (req, res) {
    var barsToFind = req.body.bars.split(',');
    // find the matching document
  };
  </code></pre>
  
  <p>Does Mongoose provide an API for this or is there a query param I can pass to Model#find to get this functionality?  I only want a document to be returned if its bar property contains all of the values in the <code>barsToFind</code> array.</p>