OpenApiNetV2Prev7

Upgrade to OpenAPI.NET v2.0.0-preview7

The OpenAPI.NET library used in ASP.NET Core OpenAPI document generation has been upgraded to v2.0.0-preview7. This version includes various bug fixes and improvements while also introducing some breaking changes. The breaking changes should only impact users that use document, operation, or schema transformers. Breaking changes in this iteration include the following:

• Entities within the OpenAPI document, like operations and parameters, are typed as interfaces. Concrete implementations exist for the inlined and referenced variants of an entity. For example, an IOpenApiSchema can either be an inlined OpenApiSchema or an OpenApiSchemaReference that points to a schema defined elsewhere in the document.
• The Nullable property has been removed from the OpenApiSchema type. To determine if a type is nullable, evaluate if the OpenApiSchema.Type property sets JsonSchemaType.Null.