title: How to create composite UNIQUE constraint in FluentNHibernate?
body: <p>I know that I can <code>Map(x =&gt; x.GroupName).WithUniqueConstraint()</code> for a single property.</p>
  
  <p>But how do create a composite unique constraint in fluent nHibernate (where the unique constraint operates on the combination of two columns)?</p>