use case: refine if and when links with the same interface endpoints if they should be created or not

[viniarck]

This is for refining if and when links with the same interface endpoints if they should be created or not.

Context:

Currently, they get created, it doesn't cause harm, but in production networks links can get looped temporarily during network maintenance. If they get discovered, network operators need to delete, and currently those kind of links don't have utility as p2p. This has been reported by AmLight engineers. This issue is for discuss use cases and the future behavior that should be supported.

[italovalcy]

For multi-access interfaces, that would make sense. We discussed about supporting multi-access interfaces in the past, so we should also consider this when deciding the approach