Team-owned resources across Nextcloud

The problem

In Nextcloud, "Shared with the team" almost always means "owned by a person, lent to the team." With the exception of Team-folders, Collectives, and Talk, resources are bound to a single user; a team is only granted access on top. That makes the team a guest in its own workspace, with important consequences:

• Off-boarding silently destroys team assets. A team is meant to outlive any member, but delete the account of the person who created a resource and it can vanish.
• Team roles don't govern resources. A team owner has no authority over a deck board owned by a member, and removing someone from the team doesn't touch what they own.

Possible solutions

• Allow all main Nextcloud resources to be owned by a team, instead of a single user.
• From each app, allow users to add team members to the team, instead of adding share recipients to resource

App specific issues

• Talk (we probably need a way to lock the participants list to the team members list)
• Activity (team filtered-activity?)
• Calendar: https://github.com/nextcloud/calendar/issues/3044
• Mail: https://github.com/nextcloud/mail/issues/572
• Deck: https://github.com/nextcloud/deck/issues/8167
• Tables
• Announcements
• Forms
• Tasks
• Polls
• Whiteboard (just stored as files)
• Notes (Collectives would cover this?)
• Collectives
• Files

Start with the app-specific issue list, especially the linked Calendar, Mail, and Deck issues, to identify which ownership and team-membership behavior is in scope. Compare those existing proposals with the unchecked apps and define a bounded resource before implementation; done requires an agreed ownership model and corresponding app behavior.