Add notifications to pipeline

[jamie-meyer]

Add Slack and email notifications to the Jenkins pipeline covering failures.

[mjemnawaz]

Added a new "Slack" stage to the pipeline on branch ISSUE-12. Will merge once SLACK_TOKEN credential is added to the Jenkins instance.

stage('Slack') {
            steps {
                slackSend baseUrl: 'https://hooks.slack.com/services/',
                channel: '#jenkins',
                color: 'good',
                message: 'Jenkins Pipline executed successfully!',
                teamDomain: 'apachenutch401',
                tokenCredentialId: 'SLACK_TOKEN'
            }
 }

[mjemnawaz]

Merged into main.