add email notify function

Former-commit-id: 2c4a16473de125cd19c6c440d98171e190786179

ci/jenkinsfile/notify.groovy

+def notify() {
+    if (!currentBuild.resultIsBetterOrEqualTo('SUCCESS')) {
+        // Send an email only if the build status has changed from green/unstable to red
+        emailext subject: '$DEFAULT_SUBJECT',
+        body: '$DEFAULT_CONTENT',
+        recipientProviders: [
+            [$class: 'DevelopersRecipientProvider'],
+            [$class: 'RequesterRecipientProvider']
+        ], 
+        replyTo: '$DEFAULT_REPLYTO',
+        to: '$DEFAULT_RECIPIENTS'
+    }
+}
+return this
+

ci/main_jenkinsfile

@@ -232,6 +232,12 @@ spec:
     }
 
     post {
+        always {
+            script {
+                def notify = load "${env.WORKSPACE}/ci/jenkinsfile/notify.groovy"
+                notify.notify()
+            }
+        }
         success {
             script {
                 updateGitlabCommitStatus name: 'CI/CD', state: 'success'