newswww: add /$MESSAGE_ID global redirector endpoint
This is the fallback for the normal WWW endpoint.
Adding this to the top-level seems to be alright, since lynx and
w3m both understand nntp://<HOSTNAME>/<Message-ID> anyways.
If newsgroup and inbox names conflict, then consider it the
fault of the original sender.
Since NewsWWW is intended to support buggy linkifiers in mail clients,
they can interpret nntp:// URLs as http://<HOSTNAME>/<Message-ID>
Inbox ordering from the config file is preserved since
commit
cfa8ff7c256e20f3240aed5f98d155c019788e3b
("config: each_inbox iteration preserves config order"),
so admins can rely on that to configure how scanning
works.
Requested-by: Konstantin Ryabitsev <konstantin@linuxfoundation.org>
cf. https://public-inbox.org/meta/
20190107190719.GE9442@pure.paranoia.local/
nntp://news.public-inbox.org/
20190107190719.GE9442@pure.paranoia.local