message: search-backend: update changeset to minor and add migration steps
diff: ---
  -'@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,
  + });
  +}
  +```
  