dispatch::request recognises Twt-Register, Twt-Help, Twt-Admit, Twt-Block and
Twt-Registration, validating values but deciding nothing: whether the sender
may do what they asked is the caller's business, as with the rest of this
module.
One command per mail. Two requests have no sensible order, and a request mixed
with a feed command would make the reply ambiguous about what took effect.
Twt-Register takes an optional nick, validated against the nick rule rather
than the path rule, since the value lands in feed metadata.
dispatch::claimed is follow_rotation's Reply-To extraction, lifted out and
documented for what it actually proves: the sender signed this URI. It does
not prove they hold the mailbox it names. follow_rotation is safe on that
alone only because it additionally demands a feed already bound to the address
and a signed chain from the key on file; a registration path has neither and
must resolve the address itself.
Twt-Help ignores any value rather than refusing one — failing a request for
help on a typo would be perverse.
Also narrows i18n's id list back to the ids looked up by name: generating it
from the catalogue made that test assert the catalogue against itself. The
reason-* ids are covered by walking the enum instead, which cannot drift.
03e54fea49