Verify DTOs against the live API

Goal: our DTOs and test payloads must match what the API really returns, so that a "passing" WireMock test means the client works in production.

Steps

1. List the endpoints to check. Take the URL builders (src/OpenUrzednik.Nbp/UrlBuilder/NbpUrlBuilderFactory.cs, NbpUrlBuilder.cs) and the DTOs in src/<Provider>/Dto/. Narrow to $ARGUMENTS if given.

2. Call the real API with the read-only curl -s and ?format=json. For NBP, cover:

   • every table (a, b, c) for both exchangerates/tables/{t} and exchangerates/rates/{t}/{code}
   • cenyzlota
   • each URL shape: latest, last/{n}, today, {date}, {from}/{to}
   • error cases: a future date, an out-of-range last/{n} (> 255 for rates and gold prices, > 67 for tables A and C, > 14 for table B), a date with no publication (weekend), a too-long range. Record the status code and the body text (NBP returns plain-text messages such as 400 BadRequest - Błędny zakres dat).

   Keep the request count low: NBP is a public service, so don't loop or hammer it.

3. Compare with the DTOs:

   • A required property missing from any real response is a bug: deserialization will fail.
   • Report extra fields we ignore, type mismatches (number vs string, date formats) and casing.

4. Compare with the WireMock tests in tests/OpenUrzednik.IntegrationTests/<Provider>/WireMock/. Flag every hand-written body that differs in shape from the real one.

5. Capture fixtures when asked, or when fixing a mismatch: save real bodies under tests/OpenUrzednik.IntegrationTests/<Provider>/Fixtures/<endpoint-shape>.json (trim long arrays to 2–3 items, keep the real structure) and load them in the WireMock tests instead of inline JSON.

6. Report a table: endpoint | status | fields in response | DTO verdict (OK / missing required / extra / type mismatch) | test payload verdict. List the limits you observed (max last/{n}, max date range, earliest date) next to the values used in Validation/.

Don't change validators based on one observation without saying so: point out differences from the documented limits and let the maintainer decide.