Add document unsubscribe link in email footer (#5762)

app/hooks/useQueryNotices.ts

@@ -0,0 +1,31 @@
+import * as React from "react";
+import { useTranslation } from "react-i18next";
+import { QueryNotices } from "@shared/types";
+import useQuery from "./useQuery";
+import useToasts from "./useToasts";
+
+/**
+ * Display a toast message based on a notice in the query string. This is usually
+ * used when redirecting from an external source to the client, such as OAuth,
+ * or emails.
+ */
+export default function useQueryNotices() {
+  const query = useQuery();
+  const { t } = useTranslation();
+  const { showToast } = useToasts();
+  const notice = query.get("notice") as QueryNotices;
+
+  React.useEffect(() => {
+    switch (notice) {
+      case QueryNotices.UnsubscribeDocument: {
+        showToast(
+          t("Unsubscribed from document", {
+            type: "success",
+          })
+        );
+        break;
+      }
+      default:
+    }
+  }, [t, showToast, notice]);
+}