title: What is the simplest way to do upsert with Ecto (MySQL)
body: <p>Doing upsert is common in my app and I want to implement the cleanest and simple way to implement upsert.</p>
  
  <ol>
  <li>Should I use fragments to implement native sql upsert?</li>
  <li>Any idiomatic ecto way to do upsert?</li>
  </ol>