title: Manual approval in GitLab CI deployment pipeline
body: <p>we've got a <strong>GitLab CI</strong> build / test / deployment pipeline and need to insert a <strong>manual approval</strong> between deployment to <em>Test</em> and promoting to <em>Prod</em>. I can't figure out how to do that. </p>
  
  <p>Ideally we would like to have a button like in <em>GoCD</em> or in <em>AWS CodePipeline</em>. However for our current project we use <em>GitLab EE</em> (ver 12.3.5-ee) hosted on our servers, not using gitlab.com, but I guess the <code>.gitlab-ci.yml</code> should be the same.</p>
  
  <p>This is a part of my current <code>.gitlab-ci.yml</code>:</p>
  
  <pre><code>stages:
    # lint, build, test, ...
    - deploy_test
    - approval
    - deploy_prod
  
  
  deploy_test:
    stage: deploy_test
    only:
      refs:
        - prod
  
    script:
      ...
  
  wait_for_approval:
    stage: approval
    # how do I do this???
  
  deploy_prod:
    stage: deploy_prod
    only:
      refs:
        - prod
  
    script:
      ...
  </code></pre>
  
  <p>Any idea?</p>