thinking about this again, after this PR

it would make more sense to specify tunnel addresses as tunnel:portal:target than tunnel:<portal_address>:target because the target shouldn't have an opinion on how you connect to the portal. Maybe you can only connect to them via websockets?

On 3rd thoughts, maybe the address should be tunnel:hmac(portal, target) since you have to know a connection address for the portal anyway, this now means the identity of the portal is not revealed (unless it's already known). That would enable fully private pubs - provided we also had implemented privater-gossip-requests