Augment Get-IshPublicationOutputContent with protocol OpenApiWithOpenIdConnect implementation

[ddemeyer]

Summary...
Get-IshPublicationOutputContent (see #126) currently only implements WcfSoapWithWsTrust/WcfSoapWithOpenIdConnect calling Baseline25.ExpandBaseline and Baseline25.CompleteBaselineByCandidateAndMode. Modernize the cmdlet by adding an OpenApiWithOpenIdConnect implementation next to it, following the switch (IshSession.Protocol) sample in AddIshFolder.cs.

The existing cmdlet and its IshObjectGroup parameter set, including -AutoCompleteMode, -Language and -Resolution, remain exactly the same, so this is backward compatible. It is only an internal change to enable an extra backend. The output objects (IshDocumentObj via IshObjects/IshMetadataField) remain the same; users of the ISHRemote library should not see a difference and get no breaking change.

Actions...

Phase 3 - REST parity for plain expand (no -AutoCompleteMode)

• Adapt GetIshPublicationOutputContent.cs to branch on IshSession.Protocol and call the OpenAPI equivalent of Baseline25.ExpandBaseline (POST /v3/Baselines/{Id}/Report/Expand in OpenApiISH30.json) when Protocol == OpenApiWithOpenIdConnect
• Map IshFields/IshRequestedMetadataField silent metadata fetch (publication output + output format) to their OpenAPI equivalents (OpenApiISH30Client.GetPublicationOutputByLanguageCardIdAsync or similar, and the output format metadata call)
• Convert the OpenAPI (json) baseline report response into the same allLngRefs/reportitem walking logic used today for the SOAP xml report
• Reuse the existing OpenAPI DocumentObj25-equivalent batch hydrate call (see Augment Get-IshDocumentObj with protocol OpenApiWithOpenIdConnect implementation #229) for the final IshDocumentObj retrieval, or add the OpenAPI variant if Augment Get-IshDocumentObj with protocol OpenApiWithOpenIdConnect implementation #229 is not yet merged

Phase 4 - REST parity for -AutoCompleteMode

• Call POST /v3/Baselines/{Id}/Report/Complete (CompleteBaseline in OpenApiISH30.json) when -AutoCompleteMode is bound and Protocol == OpenApiWithOpenIdConnect
• Map Enumerations.BaselineAutoCompleteMode to the REST enum (none/firstVersion/latestReleased/latestAvailable) using EnumConverter.ToBaselineAutoCompleteModeRest<TResult> (already added in Add cmdlet Get-IshPublicationOutputContent to return directly linked content objects of this publication #126)
• Note: the REST CompleteBaseline endpoint exposes an additional persist flag not currently surfaced by this cmdlet; that belongs to Extend Set-IshBaselineItem to update a baseline using the incoming IshDocumentObj versions #222, not this issue

Once both phases have a working OpenAPI call, human approved:

• Extend GetIshPublicationOutputContent.Tests.ps1 with comparison tests, dynamically switching $ishSession.Protocol between WcfSoapWithOpenIdConnect and OpenApiWithOpenIdConnect and back, to exercise both the SOAP and REST/OpenAPI backend with a shallow result compare