#290 feat: OpenAPI schema overrides carried to generated structs

[RAprogramm]

Closes #290

A JSONB column typed as serde_json::Value documents as a free-form object, and there was no way to say otherwise: #[schema(...)] is not a helper attribute of the derive, so writing it on an entity did not compile — and the generated DTOs would not have carried it anyway. The workaround was a hand-written duplicate of the generated struct existing only to hold the attribute.

The attribute is now accepted on a field and forwarded verbatim to every generated struct that derives utoipa::ToSchema: the create and response DTOs and the joined view. Whatever utoipa accepts works here, because nothing is parsed twice.

Two deliberate exclusions. With the api feature off nothing generated derives ToSchema, so the attribute is dropped rather than emitted onto a struct that cannot interpret it. Update DTOs never carry it: the macro rewrites their field types for PATCH semantics, so a declared value_type would contradict the type actually generated.

Covered by unit tests on the parser, a compile-pass case asserting all three generated structs implement ToSchema with an override in place, and documented in the README reference and the attribute page in all five wiki languages.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.

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