Extend `bs.link` to support link types beyond "parent" and "child"

[aksiome]

🗂️ Request Type

Feature

🧩 Feature or Module Name

bs.link

📝 Description

The current linking mechanism in bs.link is quite limited, supporting only "parent" and "child" relationships. It would be useful to support custom link types to express more complex or specific relationships between entities.

I'm not completely sure how this could be implemented yet. One suggestion was to use custom_data storage with namespaced IDs to track these links. However, if we go in that direction, it might be outside the original scope of bs.link and more appropriate for a separate module focused on generalized data relationships.