title: Swagger: I need versioning AND grouping
body: <p>Swagger with .Net 5 REST API.</p>
  <p>I have an API with hundreds of methods that necessitates the use of grouping related APIs together.  At the same time, I need to start work on a V2 version of my API.  I have spent hours trying different approaches to implement versioning AND grouping without success.</p>
  <p>I have several controllers, some for V1 and some for V2.  Can someone offer a complete example?</p>