API - Modify simple user to admin of the poll / Delegate admin on a poll

[Youcef-Volya]

⚠️ This issue respects the following points: ⚠️

• [X] I agree to follow Nextcloud's Code of Conduct.

Describe the goal you'd like to achieve

As a poll owner, I want to be able to add/modify/remove a user to be a delegate admin of the poll, using API request, because it's like that on the web interface and a route exist on the webapp.

Describe possible solutions

No response

Additional context

No response

[dartcafe]

Yep. This is missing. Completing the API and get it to non-draft state is is scheduled after the vue3 migration.