Issue Description: 

We currently run both a "stable" and a stage environment. This leads to unnecessary duplication and we can instead simply run with our stage environment as it is much closer to our production environment.

Acceptance Criteria: 

• Decide if we continue to use the AddOn process for our stage environment or revert to a kustomize overlay as we are not using the AddOn in production
• Ensure we have testing pipelines in place to verify functionality of our stage environment
• Inform notification service of the new environment and give them time to migrate
• Decommission the stable environment resources
• Inform the rest of the team of the new deployment process to stage

Additional Information: 

• This can be considered a placeholder task. Feel free to convert it into an Epic or add sub-tasks to track the work