title: Mongoose ValidatorError even though fields are provided and non-null
body: <p>I got an "interesting" issue when trying to add a new user using my API... I get the following error, even though the required fields are submitted. I can't really figure out why. I've added the relevant part of the code. Thanks.</p>
  
  <pre><code>$ curl -v http://localhost:3000/api/users --data "{ 'user_name':'xsa', 'email':'foo@bar.baz' }"
  </code></pre>
  
  <p>The error:</p>
  
  <pre><code>{"errors":{"email":{"message":"Path `email` is required.","name":"ValidatorError","properties":{"message":"Path `{PATH}` is required.","type":"required","path":"email"},"kind":"required","path":"email","$isValidatorError":true}},"_message":"User validation failed","message":"User validation failed: email: Path `email` is required.","name":"ValidationError"}
  </code></pre>
  
  <p>models/user.js</p>
  
  <pre><code>[...]
  
  user_name: {
      type: String,
      lowercase: true,
      required: true,
      index: {
        unique: true
      },
      trim: true,
      min: 3,
      max: 8
    },
    email: {
      type: String,
      lowercase: true,
      required: true
    },
  
  [...]
  </code></pre>
  
  <p>routes/user.js</p>
  
  <pre><code>router.post('/users', (req, res, err) =&gt; {
    var user = new User(req.body);
  
    user.save()
      .catch((err) =&gt; {
        res.send(err);
      });
  });
  </code></pre>