✨ feat: implement new feature for enhanced user experience

.github/instructions/api-hooks.instructions.md

@@ -0,0 +1,51 @@
+---
+name: API Hooks
+description: tibi-server hook conventions and typing.
+applyTo: "api/hooks/**"
+---
+
+# API Hooks (tibi-server)
+
+- Wrap hook files in an IIFE: `;(function () { ... })()`.
+- Always return a HookResponse type or throw a HookException type.
+- Use inline type casting with `/** @type {TypeName} */ (value)` and typed collection entries from `types/global.d.ts`.
+- Avoid `@ts-ignore`; use proper casting instead.
+- Use `const` and `let` instead of `var`. The tibi-server runtime supports modern JS declarations.
+
+## context.filter – Go object quirk
+
+`context.filter` is not a regular JS object but a Go object. Even when empty, it is **truthy**.
+Always check with `Object.keys()`:
+
+```js
+const requestedFilter =
+    context.filter &&
+    typeof context.filter === "object" &&
+    !Array.isArray(context.filter) &&
+    Object.keys(context.filter).length > 0
+        ? context.filter
+        : null
+```
+
+**Never** use `context.filter || null` – it is always truthy and results in an empty filter object inside `$and`, which crashes the Go server.
+
+## Single-item vs. list retrieval
+
+For single-item retrieval (`GET /:collection/:id`), the Go server sets `_id` automatically from the URL parameter.
+GET read hooks should therefore **not set their own `_id` filter** for `req.param("id")`;
+instead, only add authorization filters (e.g. `{ userId: userId }`).
+
+## HookResponse fields for GET hooks
+
+- `filter` – MongoDB filter (list retrieval only, or to restrict single-item retrieval)
+- `selector` – MongoDB projection (`{ fieldName: 0 }` to exclude, `{ fieldName: 1 }` to include)
+- `offset`, `limit`, `sort` – pagination/sorting
+- `pipelineMod` – function to manipulate the aggregation pipeline
+
+## API Tests (Playwright)
+
+- When creating or modifying collections/hooks: extend or create corresponding API tests in `tests/api/`.
+- Test files live under `tests/api/` and use fixtures from `tests/api/fixtures.ts`.
+- Helpers: `ensureTestUser()` (`tests/api/helpers/test-user.ts`), Admin API (`tests/api/helpers/admin-api.ts`), MailDev (`tests/api/helpers/maildev.ts`).
+- After hook changes, run only the affected API tests: `npx playwright test tests/api/filename.spec.ts`.
+- When tests fail, clarify whether the hook or the test needs adjustment – coordinate with the user.