Add domain users to conversations via API

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Feature request

Which Nextcloud Version are you currently using: (see administration page)
NextCloud version: 30.0.6.
Talk vesrion: 20.1.4

Is your feature request related to a problem? Please describe.
I have set up a Powershell script to manage conversation participants via domain groups via API. However, this only works for local users and does not work for users synced via Active Directory. However, you can add users from Active Directory from the NextCloud interface. The query to add participants is:
Invoke-RestMethod -Method Post -Headers $Headers -Uri "$CloudBaseURL/ocs/v2.php/apps/spreed/api/v4/room/$NCTalkGroupToken/participants" -Body @{newParticipant="XXXXXXXXXX";source="users"}
When specifying domain users by login/mailbox, the API returns 404; when specifying a local administrator account, the request is processed correctly and the new participant joins the conversation.

Describe the solution you'd like
Ability to add Active Directory users to conversations via API.

Describe alternatives you've considered
No.

Additional context
No.

Start at the Talk participants API endpoint named in the report and compare its behavior with the Nextcloud interface path that can add Active Directory users. Done means the API accepts a domain-synced user identifier and adds that user to the conversation instead of returning the reported 404.