Rewrite some function to get rid of the dependency on Headscale object. This allows us
to write succinct test that are more easy to review and implement.
The improvements of the tests allowed to write the removal of the tagged hosts
from the namespace as specified here: https://tailscale.com/kb/1068/acl-tags/
This call should be done quite at each modification of a server resources like RequestTags.
When a server changes it's tag we should rebuild the ACL rules.
When a server is added to headscale we also should update the ACLRules.
This commit change the default behaviour and remove the notion of namespaces between the hosts. It allows all namespaces to be only filtered by the ACLs. This behavior is closer to tailsnet.
Adrien Raffin