Fix multiple routes of same template in attribute-based routing

[tchowice]

Changes

ASP.NET instrumentation fails to extract route for attribute-based routing, if multiple HTTP methods use the same route template--a common scenario for RESTful APIs. For example:

public class WidgetsController : ApiController
{
    [Route("api/widgets/{id}")]
    public string Get(int id) {...}

    [Route("api/widgets/{id}")]
    public void Put(int id, [FromBody]string value) {...}

    [Route("api/widgets/{id}")]
    public void Delete(int id) {...}
}

In this case, the MS_Subroutes array will have multiple elements, each corresponding to a different HTTP method.

The original code only extracts the route template if there's only one element in the array. The correct thing to do is to just extract the template from the first subroute, since all subroutes have the same template.

It's not possible for MS_Subroutes array to have different templates in its elements. WebAPI would fail to route and throw an exception, if you declare multiple actions for the same method/template

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)
• Unit tests added/updated
• Appropriate CHANGELOG.md files updated for non-trivial changes
• Changes in public API reviewed (if applicable)

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: Kielek / name: Piotr Kiełkowicz (7eac47d)
• ✅ login: tchowice (1d5b33d, 7b8023c)

[Kielek]

Please sign EasyCLA. It is hard requirement to accept any contribution to this repository.

[tchowice]

Please sign EasyCLA. It is hard requirement to accept any contribution to this repository.

Thanks. Working with my company to figure this out.

[tchowice]

Please sign EasyCLA. It is hard requirement to accept any contribution to this repository.

Thanks. Working with my company to figure this out.

[tchowice]

Please sign EasyCLA. It is hard requirement to accept any contribution to this repository.

Okay, I finally got my company to sign the CLA. Please proceed with reviewing!