ParameterValue enum with fields does not follow serde rename

[spoorn]

Enum fields like allow_reserved in ParameterValue is not following the serde rename: https://github.com/GREsau/okapi/blob/d3bc6583dd828d37dc22f010ca8d51bfd1866a0a/okapi/src/openapi3.rs#L276-L298

It needs rename_all_fields specified to work on the enum fields: https://serde.rs/container-attrs.html

This causes it to fail OpenAPI spec validation