title: Dynamic _url from rails route
body: <p>In my app engine I can reference:</p>
  
  <pre><code>engine_name.app_integration_stripe_url
  </code></pre>
  
  <p>And the correct url is returned. I'd like at some point to generate this URL dynamically based on the integration being configured. This is what I thought would work, but this throws an error:</p>
  
  <pre><code>  integration_key = 'stripe'
    route_name = "app_integration_#{integration_key}_url".to_sym
    redirect_to engine_name.method(route_name).call(query_params)
  </code></pre>
  
  <blockquote>
    <p>undefined method app_integration_stripe_url for class
    ActionDispatch::Routing::RoutesProxy</p>
  </blockquote>
  
  <p>How can I generate one of these URLs dynamically?</p>