title: how do I deploy to a custom service with the appengine gradle plugin?
body: <p>I have seen all the parameters from the <a href="https://cloud.google.com/appengine/docs/standard/java/tools/gradle-reference" rel="nofollow noreferrer">documentation</a>. But none of them allow to override the <code>service</code> parameter from the generated yaml. </p>
  
  <p>I tried using <code>deployables = app.yaml</code> with the app.yaml below but it gives me a 500 error:</p>
  
  <pre><code>runtime: java7
  threadsafe: True
  api_version: '1.0'
  service: backend
  handlers:
  - url: /.*
    script: unused
    login: optional
    secure: optional
  skip_files: app.yaml
  </code></pre>
  
  <p>Any idea what I'm doing wrong ?</p>