Automate posting of release notes to VA Slack

[coreycarvalho]

User Story - Business Need

Currently, at the end of every release, a developer manually copies and pastes the release notes into Slack. In order to fully automate the CI/CD pipeline, we need to remove the manual step of copy/pasting the release notes into the VA Slack workspace.

• Ticket is understood, and QA has been contacted (if the ticket has a QA label).

User Story(ies)

As a VA Notify developer
I want automatic release note posting to VA Slack
So that I don't have to copy and paste them manually.

Additional Info and Resources

We implemented this for Oddball Slack in #1972. We need to wait for the VA to give us a webhook URL to use. This will just be a copy/paste of https://github.com/department-of-veterans-affairs/notification-api/blob/main/.github/workflows/cd-pipeline.yml#L136 using the VA Slack webhook.

Acceptance Criteria

• When the CI/CD pipeline finishes, and a new version is released to production, release notes are automatically sent to Slack
  • #va-notify-public (Office of CTO @ VA)

QA Considerations

Potential Dependencies

Slack VA webhook. We've already reached out to them. Will pull this work after we get the URL.