NSwag.MSBuild does not support API versioning or multiple routes

[phbarton]

I am using NSwag.MSBuild 11.17.12. Additionally, I am using Microsoft.AspNetCore.Mvc.Versioning 2.2.0. If I have a controller such as:

    [Authorize]
    [ApiVersion("1.0")]
    [ApiVersion("2.0")]
    [Route("v{version:apiVersion}/mycontroller")]
    public class MyController : Controller
    {
    }

The NSwag build will only generate the swagger.json file for the first version, only. Subsequent versions do not show in the swagger file.

Also, if I try to add multiple routes to a single controller, the tool fails with an exception stating that the collection contains more than one element on a .Single() call. Example controller:

    [Authorize]
    [ApiVersion("1.0")]
    [Route("notversioned/mycontroller")]
    [Route("v{version:apiVersion}/mycontroller")]
    public class MyController : Controller
    {
    }

Expectations

1. The generated swagger file would contain all versions/paths as specified with the [ApiVerion(...)] attributes, and
2. The generation tool allows for multiple routes for a single controller and generates the appropriate entries in the swagger.json file.

[RicoSuter]

I think ATM the idea is to generate one spec per version.

Ref: #1288