title: How to use multiple credentials in withCredentials in Jenkins Pipeline
body: <p>I have the following step in my declarative jenkins pipeline:
  I create script which comes from my <code>resources/</code> folder using libraryResource. This script contains credentials for my <code>autobuild</code> user and for some <code>admintest</code> user.</p>
  
  <pre><code>stage('Build1') {
                  steps {
                      node{
                          def script = libraryResource 'tests/test.sh'
                          writeFile file: 'script.sh', text: script
                          sh 'chmod +x script.sh'
                          withCredentials([usernamePassword(credentialsId: xxx, usernameVariable: 'AUTOBUILD_USER', passwordVariable: 'AUTOBUILD_PASSWD')]){
                              sh './script.sh "
                          }
  
                      }
  
                  }   
  </code></pre>
  
  <p>This works fine. I can use my <code>autobuild</code> user. Now I'm searching for the best way how I can include also the crendentials of my <code>admintest</code> user.
  Do I have to 'nest' it with a second <code>withCredentials</code> part or can I add again a <code>usernamePassword</code> 'array'?</p>