* Update NSwag URLs to current GitHub location
* Add solution for web-api-help-pages-using-swagger projects
* Bump NSwag and Swashbuckle package versions
- current and next versions
- will need to bump versions again to pick up latest Microsoft-provided features
* React to latest NSwag and Swashbuckle versions
- lots of renames and type changes (especially `string` -> `Uri`) in NSwag
- Swashbuckle now relies on Microsoft.OpenApi.Models
- disable OpenAPI doc generation in other .NET Core 2.0 project
* Remove unused namespaces
- NSwag and Swashbuckle now use common `Startup` namespaces such as Microsoft.AspNetCore.Builder
nit: sort `using`s
* remove extra comma
* Move solution file into samples folder
* Minor tweaks (#12980)
7c22abea99