docs: sunset the docs/plugins section as legacy documentation

Mark all pages in docs/plugins/ with legacy admonition banners pointing
to the appropriate new frontend system and backend system documentation.
Rename the sidebar section to "Plugins (Legacy)" and move it lower in
the navigation hierarchy. Add cross-references from the new frontend
system building-plugins guide to relevant cross-cutting topics (i18n,
analytics, feature flags, search) that still live in the legacy section.

Signed-off-by: Patrik Oldsberg <poldsberg@gmail.com>
Made-with: Cursor
This commit is contained in:
Patrik Oldsberg
2026-03-17 10:49:54 +01:00
parent 05594087b9
commit 35e130c601
22 changed files with 181 additions and 55 deletions
+6
View File
@@ -4,6 +4,12 @@ title: Plugin Development
description: Documentation on Plugin Development
---
:::caution Legacy Documentation
This page covers plugin development patterns for the **old frontend system**, including `createPlugin`, `createRoutableExtension`, and `RouteRef` from `@backstage/core-plugin-api`. For the new frontend system equivalents, see [Building Frontend Plugins](../frontend-system/building-plugins/01-index.md) and [Routes](../frontend-system/architecture/36-routes.md).
:::
Backstage plugins provide features to a Backstage App.
Each plugin is treated as a self-contained web app and can include almost any