Pull student data from PowerSchool via its API and plugin model

Verified steps

1. Create a PowerSchool Data Access plugin (a ZIP file containing plugin.xml, plugin_config.xml, and queries_root XML files); in plugin.xml enable the <oauth/> element to activate API credential generation for the plugin.
2. Install the plugin in PowerSchool at Start Page > System > System Settings > Plugin Management, then navigate to the plugin's detail page to copy the generated OAuth client ID and client secret.
3. Obtain a Bearer token by POSTing to https://your-ps-instance/oauth/access_token with Authorization: Basic base64(clientId:clientSecret) and body grant_type=client_credentials; the token is valid for one hour.
4. Call the core REST endpoints: GET /ws/v1/district/student?pagesize=100&page=1 to list students with pagination; GET /ws/v1/school/:schoolId/student to scope by school; include Accept: application/json to receive JSON rather than XML.
5. For data not exposed via the core REST API, use PowerQueries: define a named_queries.xml file in your plugin with SQL queries against the PowerSchool database, then invoke them via POST /ws/schema/table/[queryname]/count and POST /ws/schema/table/[queryname] with a JSON body containing the query arguments.
6. Handle 401 responses by refreshing the Bearer token; implement pagination using the returned @expansionData pagination metadata in the response envelope, which includes count, current, and total fields.