Refresh the session

Exchanges the session pair for a new one; the old pair stops working. Re-issued into the same workspace while the user is still a member. A refusal is `400` with the field errors as the WHOLE body (no `errors` wrapper), as on `POST /api/v1/auth/refresh-token`.

curl -X POST "https://example.com/api/v2/auth/refresh-token" \  -H "Content-Type: application/json" \  -d '{    "access_token": "string",    "refresh_token": "string"  }'