First implementation (#1)

Reviewed-on: #1

fixtures/records/policy.json

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+{"applies_to":{"basis":["subscription"],"doi_prefixes":["10.5555/"]},"at":"2026-10-05T09:00:00Z","by":"ana","format":"scienting-policy/1","id":"g6r348z7ckp4q","project":"smithlab-charges","signature":{"key":"ana","scheme":"ed25519","value":"FLg+kUV7cf0v+t8tGkYEtKdEazsqBb7X2LTqRHmMXH3h3ue/SXiegRBFxgIKff28elJSFv5EG7dK9LqvOs+PAA=="},"statement":"Our institutional agreement covers internal AI use in our own cloud account for these papers (fictional).","uses":{"ai":{"internal/tenancy":true}},"valid_until":"2027-08-31T23:59:59Z"}