title: Grails domain class validator, property must be greater than another property
body: <p>I have the following domain class in my grails project:</p>
  
  <pre><code>class Vacation {
    Date start
    Date end
  
    User vacationer
  
    static constraints = {
      start(validator: {return (it &gt;= new Date()-1)})
    }
  }
  </code></pre>
  
  <p>Is it possible to add a validator that requires end to be equal or greater than start?</p>
  
  <p>Cheers</p>