title: Odoo custom form field widget - how to display field value?
body: <p>I've created a custom widget in Odoo, and display it for a form field.
  My template looks like this:</p>
  
  <pre><code>&lt;t t-name="ImageDisplayer"&gt;
      &lt;img t-att-src="?"/&gt;
  &lt;/t&gt;
  </code></pre>
  
  <p>How can I put the field's value into the <code>&lt;img&gt;</code> tag's <code>src</code> attribute?</p>