Document in-app changelog

documentation/CHANGELOG.md

@@ -20,3 +20,4 @@
 - Added backend validation for tab-list query params (`sorting`, `pagination`, `limit/offset`, `columnfilters`) with structured `400` errors on invalid inputs for Reference, Time Unit, Time Bound, and Museum detail-tab endpoints.
 - Added tab-list API integration coverage for invalid sorting/filter payloads and pagination behavior, plus read-only Project tab unit coverage that verifies edit-only controls stay hidden without edit rights.
 - Added rollout documentation for unified `DetailTabTable` behavior, migration checklist, and known server/client filtering constraints.
+- Added a front-page changelog sourced from GitHub releases via `GET /changelog` (see `documentation/functionality/changelog.md`).

documentation/functionality/changelog.md

@@ -0,0 +1,50 @@
+# In-app Changelog (GitHub Releases)
+
+The application front page shows a **Changelog** section that is sourced from **GitHub releases** in the
+`nowcommunity/nowdatabase` repository.
+
+## Overview
+
+- Backend route: `GET /changelog`
+- Frontend: `frontend/src/components/FrontPage.tsx` fetches the route via RTK Query and renders the entries.
+- Purpose: show what has been deployed (release title + description + release creation time).
+
+## Backend
+
+### Route
+
+- `backend/src/routes/changelog.ts` exposes `GET /changelog`
+- `backend/src/services/changelog.ts` fetches GitHub releases from the GitHub REST API.
+
+### Caching and failure behavior
+
+- The backend keeps an in-memory cache with a TTL (see `CACHE_TTL_MS` in `backend/src/services/changelog.ts`).
+- If GitHub fetching fails and there is a cached value, the cached value is returned.
+
+### Authentication / rate limits
+
+- The service will use `process.env.GITHUB_TOKEN` (or `process.env.GH_TOKEN`) if present.
+- If no token is provided, unauthenticated GitHub API requests are used and may hit stricter rate limits.
+
+## Frontend
+
+- Query is defined in `frontend/src/redux/changelogReducer.ts` and hits `/changelog`.
+- The front page renders `bodyHtml` using `dangerouslySetInnerHTML`.
+  - The HTML comes from GitHub’s `application/vnd.github.v3.html+json` response format.
+  - GitHub’s rendered HTML is expected to be sanitized by GitHub; we do not add extra client-side sanitization.
+
+## Filtering “internal” notes
+
+The changelog supports a simple mechanism to hide internal-only notes:
+
+- A release is omitted entirely if its **title** starts with `Internal:`
+- Within a release description, anything after a heading `### Internal` is omitted.
+
+## How to publish a changelog entry
+
+1. Create a GitHub release in `nowcommunity/nowdatabase`.
+2. Write user-facing notes in the release title/body.
+3. Optionally include internal-only notes:
+   - Prefix the release title with `Internal:` to hide the whole release, or
+   - Add a `### Internal` section at the end of the release body to hide only that section.
+