title: Can not configure the new dunglas/mercure image
body: <p>Problem:</p>
  <p>Dunglas Mercure just upgraded this week, and has completly change, it now use a caddy web serveur solution instead of a built-in web serveur, it seems to be very cool, but now, i can not configure my dunglas/mercure image anymore...</p>
  <p><a href="https://mercure.rocks/docs/UPGRADE" rel="nofollow noreferrer">https://mercure.rocks/docs/UPGRADE</a></p>
  <p>So the problem seems to be directly related to this update, because now, the dunglas/mercure image is built from a caddy web serveur image, and where before i could just configure my image like this:</p>
  <pre><code>mercure:
      image: dunglas/mercure
      environment:
        - JWT_KEY=MySecret
        - ALLOW_ANONYMOUS=1
        - PUBLISH_ALLOWED_ORIGINS=http://localhost
        - DEBUG=1
        - CORS_ALLOWED_ORIGINS=http://localhost:8080
      ports:
        - 3000:80
  </code></pre>
  <p>Now it don't work anymore (Caddy is using his default caddyFile, which is set in the caddy web serveur image called by the dunglas/mercure image)</p>
  <p>I did not succeed to configure caddy web serveur through mercure/dunglass image (configure jwt_key, cors etc...)</p>
  <p>So i'm first wondering if there a way to configure this new image?</p>
  <p>And then, if there's no way to configure it, i'll would like to know what is the purpose of this new USELESS mercure image if we can not configure it, and have to make our own with a correctly pre-configured caddy web server?</p>