Feature Request: Add Template APIs for SPA

Overview of the Feature Request
SPA needs to be able to access the collection's list of dataset templates. Currently this is done through the ManageTemplatesPage and TemplatePage. There are no non-admin APIs to match this functionality.

This feature aims to provide a set of new endpoints for listing, creating, editing, and managing templates directly through the API.

Native APIs:
GET list of templates /api/dataverses/{dataverseAlias}/templates
POST a new template /api/dataverses/{dataverseAlias}/template with json template object (requires Permission.EditDataverse)

Existing APIs
DELETE /admin/template/{id}
GET /admin/templates
GET /admin/templates/{alias}

New API Requests:

• Edit template metadata: Updates the template’s metadata fields.
• Manage template terms: Allows adding and editing of the template’s terms section.
• Set a template as default: Marks the specified template as the default for the Dataverse.

What kind of user is the feature intended for? API User
(Example users roles: API User, Curator, Depositor, Guest, Superuser, Sysadmin)

What inspired the request?
From 2025 Q3 proposal, the goal is to enable the SPA and external API clients to manage dataset templates.

What existing behavior do you want changed?

Any brand new behavior do you want to add to Dataverse?

Any open or closed issues related to this feature request?
https://github.com/IQSS/dataverse/issues/11423
See sub-issues

Are you thinking about creating a pull request for this feature?
Help is always welcome, is this feature something you or your organization plan to implement?

Start by reviewing the existing admin template endpoints listed in the issue and the related issue at #11423, including its sub-issues. Map the requested list, create, edit, terms-management, and default-template operations to existing behavior; done means the non-admin API supports the stated operations with the required permission for creation.