SDTList (/sdt/sdts): swagger SDT model omits entity fields the API returns (deviceDisplayName, deviceId, deviceGroupId, dataSource*)

[rdmarsh]

Summary

The LM swagger SDT model (used by GET /sdt/sdts, i.e. SDTList) does not
declare the entity-identifying fields that the API actually returns. As a result,
any field projection on those fields is rejected as an "unknown field" even though
the API returns them correctly.

This is an upstream LM swagger gap, not an elm bug — elm validates -f against the
declared response schema, which is incomplete.

Affected endpoint

• SDTList — GET /sdt/sdts

Evidence

The swagger SDT definition declares only generic scheduling fields:

admin, comment, defaultValue, duration, endDateTime, endDateTimeOnLocal,
endHour, endMinute, hour, id, isEffective, minute, monthDay, sdtType,
startDateTime, startDateTimeOnLocal, timezone, type, weekDay, weekOfMonth

But the API returns these additional fields, none of which are declared on SDT
(or on the empty type subclasses ResourceSDT / ResourceGroupSDT /
DeviceDataSourceInstanceSDT):

deviceId, deviceDisplayName, deviceGroupId, deviceGroupFullPath,
dataSourceId, dataSourceName, dataSourceInstanceId, dataSourceInstanceName

These are exactly the fields needed to tell what each SDT applies to (a device,
a group, or an instance), so their omission is significant.

Reproduction

$ elm SDTList -s0 -f deviceDisplayName,startDateTime,endDateTime,comment
{"SDTList": [ ... records, including a populated "deviceDisplayName" ... ]}
Warning: unknown field: deviceDisplayName

The warning fires because deviceDisplayName is absent from the declared schema,
yet the value is present in the response. Same applies to deviceId,
deviceGroupId, deviceGroupFullPath, and the dataSource* fields.

Impact

• -f projection on these fields emits a spurious unknown field warning.
• Tooling that validates against the swagger schema (or merging stderr into the
  JSON stream) can be tripped up by the warning.
• The field still works — elm passes it through — so the practical workaround is to
  omit it from -f and let the full record come back, then pick the field
  client-side.

Notes

• Verified against an acme sandbox portal; the API returns the undeclared fields
  consistently across ResourceSDT, ResourceGroupSDT, and
  DeviceDataSourceInstanceSDT records.
• Related to the broader swagger-completeness gaps tracked in LM swagger missing standard query params on multiple endpoints #47.
• Upstream LM issue — keep open until the LM swagger SDT model is corrected; do not
  close on an elm-side workaround.