title: How to use ${currentBuild.result} to indicate "SUCCESS" not "null"
body: <p>My Jenkins declarative pipeline has the following post action:</p>
  
  <pre><code>mail to: '&lt;snip&gt;',
          subject: "Status of pipeline: ${currentBuild.fullDisplayName}",
          body: "${env.BUILD_URL} has result ${currentBuild.result}"
  </code></pre>
  
  <p>When the build succeeds the content of the email body is:</p>
  
  <pre><code>&lt;job name&gt; has result null
  </code></pre>
  
  <p>I understand that the value of ${currentBuild.result}" is null when the job succeeds, but this isn't convenient for the user. What is the recommended way of printing "SUCCESS" (or "FAILURE" etc) in the body message?</p>