List the caller's linked machines and their sync state

{  "machines": [    {      "label": "string",      "agent": "string",      "lastSynced": "2019-08-24T14:15:22Z",      "behindCount": 0    }  ]}

{  "defined": true,  "code": "UNAUTHORIZED",  "status": 401,  "message": "Authentication required or credentials invalid.",  "data": null}

{  "defined": true,  "code": "VALIDATION",  "status": 422,  "message": "The input failed domain validation.",  "data": {    "issues": [      {        "path": "string",        "message": "string"      }    ]  }}

{  "defined": true,  "code": "RATE_LIMITED",  "status": 429,  "message": "Rate limit exceeded; retry later.",  "data": {    "retryAfterSeconds": -9007199254740991  }}