title: Can I create unique-compound constraints on eve schema definition?
body: <p>I would like to know if it is possible to create a unique constraint into an <code>eve</code> schema definition, between two or more fields of a document, instead of only one as shown on Eve's <a href="http://python-eve.org/config.html#schema-definition" rel="nofollow">schema definition documentation</a>,</p>
  
  <p>I want the same behavior as creating a <a href="https://docs.mongodb.com/manual/core/index-unique/#unique-compound-index" rel="nofollow">Unique Compound Index</a> directly on <code>mongodb</code>, but on the <code>eve</code> API level.</p>