title: how to check if a filename contains uid in firebase storage security rules?
body: <p>I want to make  a rules in my firebase storage, and I want the filename of image stored in firebase storage contains uid of its uploader. usually in programming language I use <code>.contains</code> to check</p>
  
  <pre><code>service firebase.storage {
    match /b/{bucket}/o {
  
      match /eventThumbnail/{imageID} {
        allow create: if request.resource.name.contains(request.auth.uid)
      }
    }
  }
  </code></pre>
  
  <p>is this rules valid ? I can't find documentation about using contains in firebase storage security rules documentation. actually the rules is more complex, I still search what makes I fail to create an image, and I suspect that rules is not valid</p>