title: Match string with values from array in express-validation
body: <p>I am using express-validator to validate input to my API, but I have some problems understanding the matches function. I basically need to be able to figure out if a string matches any of the values in an array of accepted values, like shown below, but it doesn't seem to work. Any suggestions?</p>
  
  <pre><code>var schema = {
    "role": {
      in: 'body',
      matches: {
        options: ["administrator", "editor", "contributor", "user"],
        errorMessage: "Invalid role"
      }
    }
  }
  
  req.check(schema)
  </code></pre>