search-backend: update changeset to minor and add migration steps

Signed-off-by: MT Lewis <mtlewis@users.noreply.github.com>

.changeset/pink-spoons-hope.md

@@ -1,5 +1,25 @@
 ---
-'@backstage/plugin-search-backend': patch
+'@backstage/plugin-search-backend': minor
 ---
 
-Add support for filtering search results according to visibility.
+**BREAKING** Added three additional required properties to `createRouter` to support filtering search results based on permissions. To make this change to an existing app, add the required parameters to the `createRouter` call in `packages/backend/src/plugins/search.ts`:
+
+```diff
+export default async function createPlugin({
+  logger,
++  permissions,
+  discovery,
+  config,
+  tokenManager,
+}: PluginEnvironment) {
+  /* ... */
+
+  return await createRouter({
+    engine: indexBuilder.getSearchEngine(),
++    types: indexBuilder.getDocumentTypes(),
++    permissions,
++    config,
+    logger,
+  });
+}
+```