# What this PR does
add a new endpoint, `GET /maintenance-mode/`, which returns either a
string message pulled from the
`CURRENTLY_UNDERGOING_MAINTENANCE_MESSAGE` env var, or `None` + update
the UI to conditionally show this message if it is set
<img width="1321" alt="Screenshot 2023-05-10 at 11 28 16"
src="https://github.com/grafana/oncall/assets/9406895/833a77fb-3a90-4f9f-88d6-dae0d98d99d4">
## Checklist
- [x] Unit, integration, and e2e (if applicable) tests updated
- [x] Documentation added (or `pr:no public docs` PR label added if not
required) (N/A)
- [x] `CHANGELOG.md` updated (or `pr:no changelog` PR label added if not
required)
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