An API reference and rationale for whoever picks this up next. The
endpoints are the easy half; what is not obvious from reading the code is
why an ack is only published after the commit, why a duplicate counts as
a success, and why is_delta false on a filtered catalogue empties a
shop's shelf. Those are written down here because each one costs a shop
money when someone changes it without knowing.
Covers the GET endpoints in full — request parameters, real response
shapes, and the cases that surprise people: values coming back as
strings from a Redis hash, a quiet till answering 200 rather than 404,
and a bill at another outlet returning 404 even though the reference is
valid.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
