Storage seam for OID4VCI pre-authorized codes.

Attesto.PreAuthorizedCode generates and validates a pre-authorized code, but it never decides where the code lives. A host implements this behaviour over whatever store fits (Postgres, Redis, ETS); Attesto.PreAuthorizedCodeStore.ETS is a ready single-node implementation.

The single-use contract

take/1 MUST be atomic: it returns the record for code_hash and removes it in one indivisible step, so two concurrent redemptions of the same pre-authorized code cannot both succeed. A store that let take/1 race would let a captured code be replayed. A SQL implementation uses DELETE ... WHERE code_hash = $1 RETURNING ...; an ETS implementation uses :ets.take/2.

The code is consumed by take/1 even if Attesto.PreAuthorizedCode then rejects the redemption because it is expired or the presented PIN is wrong. A failed validation therefore burns the code and denies repeated attempts against a captured code.

Record fields

A stored record contains:

• :code_hash - the Attesto.Secret.hash/1 of the code (the key).
• :data - the bound issuance context.
• :expires_at - absolute expiry, unix seconds.