title: Spring validation for list of accepted string values
body: <p>Is there a <strong>validation annotation</strong> for <strong>Spring</strong> that will do something like:</p>
  
  <pre><code>@ValidString({"US", "GB", "CA"})
  final String country;
  </code></pre>
  
  <p>and validate that the string is one of the supported values in the array?</p>