title: How to require at least one of two parameters in OpenAPI?
body: <p>I'm using OpenAPI 3 and have two query parameters, at least <em>one</em> of which is required but it doesn't matter which.</p>
  
  <p>I.e., as sudocode:</p>
  
  <pre><code>if parameter_1 OR parameter_2:
      do stuff
  else:
      error
  </code></pre>
  
  <p>Is this possible in OpenAPI 3? There's no mention of it in the spec as far as I can see, or the JSON Schema spec either.</p>