Blocklist mechanism

[maurerle]

We currently do not have a blocklisting mechanism.
It might come in handy, if some nodes are behaving weird.

To do this, there should be an easy way to move a node to a quarantine domain or block it entirely.

Keys are typically added through this:
https://github.com/ffac/ff-supernode/blob/main/playbooks/roles/ff.wgbroker/templates/broker.py

• changing the nodename leads to a different file name, this should be changed, to a way that duplicates in the public key are detected
• there should be an easy mechanism to add keys to a quarantine or blocklist. Moving a key to a blocklist folder might be enough for the broker, but we have to see if the wg_link behaves fine with that as well