title: Can you set a partial schema for an object in mongoosejs?
body: <p>Can you set a partial schema for an object in mongoosejs?  Say I have a person object and I want to validate that it always has a first_name and last_name field.  But I also want to allow users to save other fields of their choosing. Say I have the following schema:</p>
  
  <pre><code>var userSchema = new mongoose.Schema({
    first_name  : { type: String, required: "first name required" }
    last_name   : { type: String, required: "last name required" }
  })
  </code></pre>
  
  <p>But I want the app to be able to post this:</p>
  
  <pre><code>{
    first_name: "john",
    last_name: "doe",
    field_not_in_schema: "info"
  }
  </code></pre>
  
  <p>Is that possible?</p>