[tor-onions] Onion v2 HSDir Support (ref: v3 prop224) [was: fishy fingerprint patterns]

[grarpamp]

> relays have a rather distinct signup and fingerprint pattern
> usually seen for onion attacks.
> ...
> a) If you are an .onion operator I'd like to encourage you to switch to onion
> services version 3
> ...
> so we can start
> ...
> b) dropping onion version 2 services eventually.

These are two separate things not necessarily tied together,
thus split for clarity as above.

The former a) is up to the onion operator based on their needs.
If they have no need for v2, or need v3, they can or should
switch to v3, indeed.

The latter b) is a feature that some users and operators
in and for onionspace explicitly choose and depend on
to support common apps, and thus would definitely not
like to see yanked out from under them.
Better instead to advertise and update the default onion
semantics for [new] users to v3, and continue support
and backport doable features to v2 until time below...

Node operators (tor-relays) would continue offering
v2 HSDir support module until such time as the reasons
for choosing v2 by those above are supported in v3 or vN.

See the threads on this subject on tor-talk, tor-onions,
and tickets for more.

[CC for inclusion, move there if not relay specific]