Draft: Acquire user_id from assignment destination

Link assignments to "workgroups" (or teams) by treating them as users

In some use cases, assignments need to be associated with a workgroup (consider it similar to a user) so that its members inherit access to the objects the workgroup owns.

This change treats a 'workgroup' (or organisation in some cases) as a user-like entity that can create and own objects, with ownership and access shared across its members.

A user_id is added to avoid the need for additional reference or codification syncing, simplifying the implementation.

This approach supports scenarios where an organization (or group) creates objects and shares them with its users.