Reflect model state validation attributes in resource object schemas

[maurei]

The usage of RequiredAttribute on a resource field translates to a property needing to be listed as required, see required properties. This is currently already supported in the OpenApi integration, but requires more thorough testing.

Further investigation is required to see whether other model state validation attributes are associated to similar options in an OAS.

[bkoelman]

See https://learn.microsoft.com/en-us/aspnet/core/mvc/models/validation#built-in-attributes and https://swagger.io/docs/specification/data-models/data-types/.