title: Form action with variable not valid after update to 1.2
body: <p>I was generating a form action in my previous version of <code>AngularJS</code> using this code:</p>
  
  <pre><code>&lt;form action="{{ api }}/products/image"&gt;
  </code></pre>
  
  <p>However, I just updated and now that apparently is too loose.</p>
  
  <blockquote>
    <p>Error while interpolating: {{ api }}/products/image
    Strict Contextual Escaping disallows interpolations that concatenate multiple expressions when a trusted value is required.</p>
  </blockquote>
  
  <p>How do I achieve the same functionality in <code>1.2.4</code>?</p>