Support maintenance mode

[junminahn]

Description

• Display a maintenance page whenever backend or infrastructure maintenance is required.

Technical Details

• Create a separate NGINX app (container) with a basic HTML page to serve as the maintenance page.
• Add a dedicated Deployment Helm chart to switch between the maintenance pod and the application pod using a Helm value toggle (boolean).
• Implement a GitHub Action dispatcher to manage maintenance mode by environment:
  • Provide a dropdown for selecting the environment.
  • Ensure the Helm chart preserves the current values, overriding only the maintenance flag when toggled.

Definition of Done (DOD)

• Maintenance mode can be toggled via the GitHub dispatcher.

[junminahn]

@Kolezhanchik https://github.com/bcgov/sso-keycloak/tree/dev/docker/maintenance-page

[Kolezhanchik]

let's break it down:

• maintenance-app with its deployment pipeline.
• helm files
• toggle dispatcher