Get Transaction

Retrieves a specific transaction by transaction ID for the authenticated exchange app. **Authentication:** - **REQUIRED**: Provide client_id and client_secret via: - Basic Auth: `Authorization: Basic base64(client_id:client_secret)` - The `exchange_app_id` is automatically derived from authenticated credentials (not required in request) **Query Parameters:** - `transaction_id` (required): The transaction ID to lookup - `view` (optional): **Default is `slim`** (minimized payload: trimmed `qr_data`, deduplicated top-level `recipient_*` when `recipient` is present). Pass `view=full` for the **legacy full** sanitized shape (full `qr_data` and duplicate flat fields). **Response:** - `transaction`: Sanitized transaction object (if found and belongs to authenticated exchange_app_id) - **Note:** Responses are sanitized: `provider` and `provider_tx_id` are removed for security, and any field whose name starts with `_` (internal server-only data) is never returned. **Returns 404 if transaction not found or doesn't belong to the authenticated exchange_app_id**