Grouped Notifications UI (#30440)

Co-authored-by: Eugen Rochko <eugen@zeonfederated.com>
Co-authored-by: Claire <claire.github-309c@sitedethib.com>

app/javascript/mastodon/actions/notifications_migration.tsx

@@ -0,0 +1,18 @@
+import { createAppAsyncThunk } from 'mastodon/store';
+
+import { fetchNotifications } from './notification_groups';
+import { expandNotifications } from './notifications';
+
+export const initializeNotifications = createAppAsyncThunk(
+  'notifications/initialize',
+  (_, { dispatch, getState }) => {
+    // eslint-disable-next-line @typescript-eslint/no-unsafe-call, @typescript-eslint/no-unsafe-member-access
+    const enableBeta = getState().settings.getIn(
+      ['notifications', 'groupingBeta'],
+      false,
+    ) as boolean;
+
+    if (enableBeta) void dispatch(fetchNotifications());
+    else dispatch(expandNotifications());
+  },
+);