## Summary
Ports the connector (data source) management endpoints that power
`web/src/pages/user-setting/data-source/` from Python
(`api/apps/restful_apis/connector_api.py`) to Go. Previously only `GET
/connectors` (list) was implemented in Go; this adds the rest of the
lifecycle.
Closes#15273 (subtask of #15240).
## Endpoints implemented
All under base path `/api/v1` (mirrors the Python routes):
| Method | Path | Description |
|--------|------|-------------|
| POST | `/connectors/{connector_id}/test` | Validate stored credentials
|
`GET /connectors` (list) was already present and is unchanged.
---------
Co-authored-by: Jin Hai <haijin.chn@gmail.com>