Co-signed completion receipt. The consumer signs the
canonicalized JSON of (lease_id, provider_npub, consumer_npub, duration_paid, duration_delivered, success_flag, payment_proof, version); the provider returns a provider_co_signature over
the same bytes; the receipt event carries both.
Per-consumer metadata the scoring function consults. Real
observatory builds this from the consumer’s first-seen Nostr
activity; tests can stub it directly.
The Cashu spend proof carried by a receipt. Captured by the
provider at redemption (Unit 1) and pasted verbatim into the
receipt the provider co-signs. Aggregators verify this against
the mint’s published keys before counting the receipt.
Score a single provider against the receipt set in receipts.
Returns a non-negative score; magnitude is the sum of weighted
success flags from receipts that survive every filter.