Web API conventions - Rich Swagger support without attributes

[Rick-Anderson]

aspnet/Mvc#6870, aspnet/Mvc#6784

Related Resources:

• ASP.NET Community Standup: https://www.youtube.com/watch?v=zr4Btou3H8c&list=PL1rZQsJPBU2StolNg0aqvQswETPcYnNKL&index=0
• ASP.NET Core 2.1 Roadmap: MVC - https://blogs.msdn.microsoft.com/webdev/2018/02/02/asp-net-core-2-1-roadmap/#mvc
• ASP.NET Core 2.1.0-preview1: Improvements for building Web APIs: https://blogs.msdn.microsoft.com/webdev/2018/02/27/asp-net-core-2-1-web-apis/

Docs to update:

• Create a Web API with ASP.NET Core and VS for Windows
• Create a Web API with ASP.NET Core and VS for macOS
• Create a Web API with ASP.NET Core MVC and Visual Studio Code on Linux, macOS, and Windows
• Get started with NSwag
• Get started with Swashbuckle
  • Update to from Swashbuckle 1.x to 2.x
  • Update to ASP.NET Core 2.1

Docs to create under the new Web API TOC node:

• ActionResult<T> reference
• [ApiController] attribute reference

[guardrex]

I'll add the small blurb here from the '2.1.0-preview2 now available' blog post:

Improvements to [ApiController] parameter binding

Applying [ApiController] to your controller sets up convenient conventions for how parameters get bound to request data. In Preview 2 we’ve made a number of improvements to how these conventions work based on feedback:

• [FromBody] will no longer be inferred for complex types with specific semantics, like CancellationToken
• Multiple [FromBody] parameters will result in an exception
• When there are multiple routes for an action parameters that match any route value will be considered [FromRoute]

There's a full example in the roadmap post at https://blogs.msdn.microsoft.com/webdev/2018/02/02/asp-net-core-2-1-roadmap/#mvc.