Support ASP.NET Core 2.2 Default Parameter Value in API Explorer

[commonsensesoftware]

The ASP.NET Core API Explorer design did not include metadata to describe whether a parameter is required and what the default value is, unless it was defined as a route parameter. ApiParameterDescription was updated in ASP.NET Core 2.2 to include new properties to support this information.

Requirements

• Support ApiParameterDescription.IsRequired
• Support ApiParameterDescription.DefaultValue
• Fix ApiParameterDescription.RouteInfo so that ApiParameterRouteInfo.DefaultValue is only used when the value actually a route parameter (ex: versioning by URL segment)