Closes#2421.
I am of the opinion that the spec is easier to read than this though,
and we shouldn't really explain this here other than that we use a variant
of station to station protocol, with X25519 for the diffie hellman, and we
describe the related security properties.
* addr_book_strick=false on local nets
* link to spec
* spec: remove TODO, see #1749 instead
* spec: make issues from TODOs
* update docs on addr_book_strict option
As we didn't hear any voices requesting this feature, we removed the
option to disable it and always have peer connection auth encrypted.
closes#1518
follow-up #1325