$bulkdata-status needs to indicate when no data was exported

[kmbarton423]

Is your feature request related to a problem? Please describe.
Ran an $export using _type and _typeFilter that I did not match any data so nothing was exported.
Ran $bulkdata-status to for the associated jobId.

{ "transactionTime": "2021-08-10T21:14:53.311Z", "request": "https://localhost:9443/fhir-server/api/v4/Patient/$export?_type=Encounter&_typeFilter=Encounter?status=active", "requiresAccessToken": false }

The status above left me guessing.

Describe the solution you'd like
I would like to see some indication returned by $bulkdata-status that the job finished successfully and no data was exported.

Describe alternatives you've considered
Maybe a return code would be better but I don't see this as a failure.

[lmsurpre]

Options:
A. empty array
B. a separate field with an OperationOutcome to explain that everything worked but there was nothing to export

The response body is defined at https://hl7.org/fhir/uv/bulkdata/export/index.html#response---complete-status
Proposal: include an empty array and an extension that has an OperationOutcome with the detaiils

[kmbarton423]

Confirmed empty array and extension now returned:

{ "transactionTime": "2021-08-24T15:13:02.866Z", "request": "https://localhost:9443/fhir-server/api/v4/Patient/$export?_type=Encounter&_typeFilter=Encounter?status=active", "requiresAccessToken": false, "output": [], "extension": { "outcome": { "resourceType": "OperationOutcome", "issue": [ { "severity": "information", "code": "informational", "details": { "text": "No Data Exported" } } ] } } }