feat: page update notifications (#2074)

* feat: watchers notification and email preferences

* fix: email copy

* digests

* clean up

* fix

* clean up

* move backlinks queue-up to history processor

* fix

* fix keys

* feat: group notifications

* filter

* adjust email digest window

apps/client/src/features/page/queries/watcher-query.ts

@@ -0,0 +1,43 @@
+import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
+import {
+  watchPage,
+  unwatchPage,
+  getWatchStatus,
+} from "@/features/page/services/watcher-service";
+import { notifications } from "@mantine/notifications";
+import { useTranslation } from "react-i18next";
+
+const WATCHER_KEY = "watcher";
+
+export function useWatchStatusQuery(pageId: string) {
+  return useQuery({
+    queryKey: [WATCHER_KEY, pageId],
+    queryFn: () => getWatchStatus(pageId),
+    enabled: !!pageId,
+    staleTime: 60_000,
+  });
+}
+
+export function useWatchPageMutation() {
+  const queryClient = useQueryClient();
+  const { t } = useTranslation();
+  return useMutation({
+    mutationFn: (pageId: string) => watchPage(pageId),
+    onSuccess: (_data, pageId) => {
+      queryClient.setQueryData([WATCHER_KEY, pageId], { watching: true });
+      notifications.show({ message: t("You are now watching this page") });
+    },
+  });
+}
+
+export function useUnwatchPageMutation() {
+  const queryClient = useQueryClient();
+  const { t } = useTranslation();
+  return useMutation({
+    mutationFn: (pageId: string) => unwatchPage(pageId),
+    onSuccess: (_data, pageId) => {
+      queryClient.setQueryData([WATCHER_KEY, pageId], { watching: false });
+      notifications.show({ message: t("You are no longer watching this page") });
+    },
+  });
+}