A delegate retrying with one `Idempotency-Key` across two people's records met
itself in one cell. The cache tuple was `(caller, key, method, path)`, so the
second record's request replayed the first record's cached 201: the handler
never ran, no row was written for the second person, and the caller was told it
had been — with the other person's id in the body. Nothing errored and nothing
logged a conflict, and five of the write verbs about to become delegable are
wrapped here.
Fold the claimed record into the `key` component, centrally, once. Not into
`userId`: that column is a foreign key to `users` with a cascade behind it and
cannot hold a composite. It keeps naming the caller, which is what makes two
delegates on one record two cells for free. The separator is a byte the key
validator refuses, so a caller cannot hand-craft a key into a cell belonging to
a request they are not making.
A request with no acting account keys byte-for-byte as it did before, so a
client that never heard of sharing cannot be affected.
Accepted and pinned by test: the fold uses the CLAIM, before the grant check,
so within the 24h window a delegate whose access has ended can still replay a
key they had already completed. They receive bytes they already had, nothing
new is written, and a fresh key from them is refused because that request
reaches the handler.
Both frozen surfaces move in this diff. The claim reader gains a guard leg
freezing its consumers, since an unchecked claim is exactly the value a future
caller must not mistake for permission.
Marc-André Bombeck
c7960d726d