Adds an external identifier for an existing job. Include the string value of the new external identifier in the message body.
You cannot change an existing external identifier with another 
POST request. The Toast platform uses this external 
identifier as one of the unique, persistent identifiers for a 
job record.
The JSON string value of the externalId for the job 
record. Wrap the value in double quotation marks to make it 
valid JSON syntax.
Returns the updated job record.
"MyToastNamingAuthority:9876543210"{- "guid": "string",
- "entityType": "string",
- "externalId": "string",
- "createdDate": "2019-08-24T14:15:22Z",
- "modifiedDate": "2019-08-24T14:15:22Z",
- "deletedDate": "2019-08-24T14:15:22Z",
- "title": "string",
- "deleted": true,
- "wageFrequency": "HOURLY",
- "defaultWage": 0,
- "tipped": true,
- "code": "string",
- "excludeFromReporting": true
}