Address review follow-ups on PR #3568:
- Extract the controller's withoutThemeFields and applyDefaultTheme helpers from a private class field into a standalone module (controllers/statusPageThemeFlag.ts) so they can be tested without a controller harness; the controller is now a one-line consumer
- Add 9 unit tests covering both helpers (test/unit/controllers/statusPageThemeFlag.test.ts): no-mutation guarantees, partial inputs, all-fields-preserved verbatim, override-with-defaults semantics, and "page has no theme set yet" — the flag-off path is now exercised in both directions
- Expand the comment over withoutThemeFields to spell out why the strip is silent rather than a 400: this is an ops kill switch, not API semantics; clients shouldn't need to know whether themes are disabled today
Two caveats called out in review that this commit does NOT change:
- Mongoose `default:` directives only inject during hydration, not on partial updates. Legacy documents updated with `findOneAndUpdate` still won't have `theme` / `themeMode` written to Mongo. They render as defaults on read because the schema injects them — functionally equivalent, but the DB will hold a mix of present and absent fields indefinitely. Acceptable per the original commit intent.
- docs/plans/status-page-themes.md (304 lines) covers both backend and frontend work for the themes feature. It lives in this PR as the design artefact that drove both branches; moving it for purity would break the "where did this come from?" trail. Leaving it in.
- StatusPage Mongoose model: import DEFAULT_STATUS_PAGE_THEME / DEFAULT_STATUS_PAGE_THEME_MODE from types/statusPage so the four sources of the default literal stay locked together
- openapi.json: add explicit "default" alongside the enum on StatusPageTheme and StatusPageThemeMode component schemas; documentation already mentioned the defaults but the JSON didn't carry them
- statusPageController: add JSDoc-style comments above withoutThemeFields and applyDefaultTheme spelling out the asymmetric strip-on-write / force-on-read semantics so the next reviewer doesn't have to re-derive the design
Server-side, return 200 with success: false and a friendly message when sendTestNotification reports failure (the underlying call already swallows the error); reserve real 500s for unexpected exceptions.
Client-side, teach usePost to honour the response body's success flag so success:false flips the toast to error without throwing through axios. Also tidy the toast container: drop icons, no wrapping, single-line ellipsis with a sensible max-width that hugs short messages.
## Changes
- Add `theme` (refined | modern | bold | editorial, default "refined") and
`themeMode` (auto | light | dark, default "auto") fields to the StatusPage
Mongoose model and the shared `StatusPage` type.
- Extend the create/update Zod validator to accept both fields optionally.
- Map both fields in the repository's `toEntity` so GET responses include them.
- Document both fields in the create and update endpoints in `openapi.json`.
- Add `STATUS_PAGE_THEMES_ENABLED` env var (default `true`) wired through
`SettingsService` for ops-level rollback. When disabled, the controller
strips theme fields on write and forces defaults on read.
## Notes
- No migration needed; Mongoose applies defaults for legacy documents.
- Controller short-circuits to zero-cost when the feature flag is on.
- `DEFAULT_STATUS_PAGE_THEME` / `DEFAULT_STATUS_PAGE_THEME_MODE` constants
exported so the frontend PR can consume the same values.
gorkem-bwl
Alex Holliday
ashu130698