pkg: Update next to v15 (#3256)

* pkg: Update `next` to v15

* pkg: Update demo package

---------

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>
Co-authored-by: Nathaniel Tucker <[email protected]>

docs/core/api/Controller.md

@@ -151,10 +151,10 @@ post.pk();
 
 ##### true
 
-- Resolves _before_ [committing](https://react.dev/learn/render-and-commit#step-3-react-commits-changes-to-the-dom) Reactive Data Client cache updates.
+- Resolves _before_ [committing](https://react.dev/learn/render-and-commit#step-3-react-commits-changes-to-the-dom) Reactive Data Client cache updates. (React 16, 17)
 - Each call will always cause a new fetch.
 
-##### undefined
+##### false | undefined
 
 - Resolves _after_ [committing](https://react.dev/learn/render-and-commit#step-3-react-commits-changes-to-the-dom) Reactive Data Client cache updates.
 - Identical requests are deduplicated globally; allowing only one inflight request at a time.

examples/nextjs/app/[userId]/layout.tsx

@@ -2,13 +2,13 @@ import Link from 'next/link';
 
 import UserSelection from '@/components/todo/UserSelection';
 
-export default function TodoLayout({
-  children,
-  params,
-}: {
+export default async function TodoLayout(props: {
   children: React.ReactNode;
-  params?: { userId: number };
+  params?: Promise<{ userId: number }>;
 }) {
+  const params = await props.params;
+  const { children } = props;
+
   return (
     <>
       <title>NextJS + Reactive Data Client = ❤️</title>

examples/nextjs/app/[userId]/page.tsx

@@ -1,5 +1,7 @@
 import TodoList from '@/components/todo/TodoList';
 
-export default function TodoPage({ params }: { params: { userId: number } }) {
-  return <TodoList {...params} />;
+export default async function TodoPage(props: {
+  params: Promise<{ userId: number }>;
+}) {
+  return <TodoList {...await props.params} />;
 }