Remove experimental.serverIslands flag (#11991)

* Remove experimental.serverIslands flag

* update link to the guide

* Add changeset

* Update packages/astro/src/core/errors/errors-data.ts

Co-authored-by: Sarah Rainsberger <sarah@rainsberger.ca>

* Update packages/astro/src/core/errors/errors-data.ts

Co-authored-by: Sarah Rainsberger <sarah@rainsberger.ca>

---------

Co-authored-by: Sarah Rainsberger <sarah@rainsberger.ca>

.changeset/dry-lamps-smile.md

@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Update error link to on-demand rendering guide

packages/astro/src/core/errors/errors-data.ts

@@ -415,7 +415,7 @@ export const AdapterSupportOutputMismatch = {
 /**
  * @docs
  * @see
- * - [Server-side Rendering](https://docs.astro.build/en/guides/server-side-rendering/)
+ * - [On-demand Rendering](https://5-0-0-beta.docs.astro.build/en/guides/on-demand-rendering/)
  * @description
  * To use server islands, the same constraints exist as for sever-side rendering, so an adapter is needed.
  */
@@ -423,7 +423,7 @@ export const NoAdapterInstalledServerIslands = {
 	name: 'NoAdapterInstalledServerIslands',
 	title: 'Cannot use Server Islands without an adapter.',
 	message: `Cannot use server islands without an adapter. Please install and configure the appropriate server adapter for your final deployment.`,
-	hint: 'See https://docs.astro.build/en/guides/server-side-rendering/ for more information.',
+	hint: 'See https://5-0-0-beta.docs.astro.build/en/guides/on-demand-rendering/ for more information.',
 } satisfies ErrorData;
 /**
  * @docs

packages/astro/src/types/public/config.ts

@@ -1603,71 +1603,6 @@ export interface AstroUserConfig {
 		 */
 		clientPrerender?: boolean;
 
-		/**
-		 * @docs
-		 * @name experimental.serverIslands
-		 * @type {boolean}
-		 * @default `false`
-		 * @version 4.12.0
-		 * @description
-		 *
-		 * Enables experimental Server Island features.
-		 * Server Islands offer the ability to defer a component to render asynchronously after the page has already rendered.
-		 *
-		 * To enable, configure an [on-demand server rendering `output` mode](https://docs.astro.build/en/basics/rendering-modes/#on-demand-rendered) with an adapter, and add the `serverIslands` flag to the `experimental` object:
-		 *
-		 * ```js
-		 * {
-		 *   output: 'hybrid', // or 'server'
-		 *   adapter: nodejs({ mode: 'standalone' }),
-		 *   experimental: {
-		 *     serverIslands: true,
-		 *   },
-		 * }
-		 * ```
-		 *
-		 * Use the `server:defer` directive on any Astro component to delay initial rendering:
-		 *
-		 * ```astro "server:defer"
-		 * ---
-		 * import Avatar from '~/components/Avatar.astro';
-		 * ---
-		 * <Avatar server:defer />
-		 * ```
-		 *
-		 * The outer page will be rendered, either at build time (`hybrid`) or at runtime (`server`) with the island content omitted and a `<script>` tag included in its place.
-		 *
-		 * After the page loads in the browser, the script tag will replace itself with the the contents of the island by making a request.
-		 *
-		 * Any Astro component can be given the `server: defer` attribute to delay its rendering. There is no special API and you can write `.astro` code as normal:
-		 *
-		 * ```astro
-		 * ---
-		 * import { getUser } from '../api';
-		 *
-		 * const user = await getUser(Astro.locals.userId);
-		 * ---
-		 * <img class="avatar" src={user.imageUrl}>
-		 * ```
-		 *
-		 * #### Server island fallback content
-		 *
-		 * Since your component will not render with the rest of the page, you may want to add generic content (e.g. a loading message) to temporarily show in its place. This content will be displayed when the page first renders but before the island has loaded.
-		 *
-		 * Add placeholder content as a child of your Astro component with the `slot="fallback"` attribute. When your island content is available, the fallback content will be replaced.
-		 *
-		 * The example below displays a generic avatar as fallback content, then animates into a personalized avatar using view transitions:
-		 *
-		 * ```astro
-		 * <Avatar server:defer>
-		 *   <svg slot="fallback" class="generic-avatar" transition:name="avatar">...</svg>
-		 * </Avatar>
-		 * ```
-		 *
-		 * For a complete overview, and to give feedback on this experimental API, see the [Server Islands RFC](https://github.com/withastro/roadmap/pull/963).
-		 */
-		serverIslands?: boolean;
-
 		/**
 		 * @docs
 		 * @name experimental.contentIntellisense