List billable seats

{  "seats": [    {      "user": {        "id": "497f6eca-6276-4993-bfeb-53cbbbba6f08",        "handle": "string",        "displayName": "string",        "avatarUrl": "string"      },      "reasons": [        {          "kind": "org-role",          "role": "owner"        }      ]    }  ]}

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

{  "defined": true,  "code": "FORBIDDEN",  "status": 403,  "message": "You do not have permission to perform this action.",  "data": null}

{  "defined": true,  "code": "NOT_FOUND",  "status": 404,  "message": "The requested resource does not exist.",  "data": {    "resource": "string"  }}

{  "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  }}