title: Mongoose (mongo), copy a document
body: <p>Trying to copy a document. First I find it. Then removing the _id. Then inserting it. But the calculation._id is still there. So I get a duplication error thrown. What am I doing wrong?   </p>
  
  <pre><code>mongoose.model('calculations').findOne({calcId:req.params.calcId}, function(){
        if(err) handleErr(err, res, 'Something went wrong when trying to find calculation by id');
  
        delete calculation._id;
        console.log(calculation); //The _.id is still there
        mongoose.model('calculations').create(calculation, function(err, stat){
          if(err) handleErr(err, res, 'Something went wrong when trying to copy a calculation');
          res.send(200);
        })
      });
  </code></pre>