[AzureMonitorexporter] fix operation name

[TimothyMothra]

When using Asp.Net Core Routing rules, our Exporter is currently recording the full pattern as the Operation Name.
This means that requests to different Controllers or Actions will show identical Operation Names, as shown in this screenshot.

This can be reproduced in an MVC app configured like this:

app.MapControllerRoute(
    name: "default",
    pattern: "{controller=Home}/{action=Index}/{id?}");

My test app has a HomeController and CustomerController. Regardless which controller is invoked, The url.path shows the correct Controller/Action. The http.route shows the configured pattern.

• https://localhost:44311/Home/Index

  Activity.ActivitySourceName: Microsoft.AspNetCore
  Activity.DisplayName:        GET {controller=Home}/{action=Index}/{id?}
  Activity.Kind:               Server
  Activity.Tags:
      server.address: localhost
      server.port: 44311
      http.request.method: GET
      url.scheme: https
      url.path: /
      network.protocol.version: 2
      http.route: {controller=Home}/{action=Index}/{id?}
      http.response.status_code: 200
  

• https://localhost:44311/Customer/Index

  Activity.ActivitySourceName: Microsoft.AspNetCore
  Activity.DisplayName:        GET {controller=Home}/{action=Index}/{id?}
  Activity.Kind:               Server
  Activity.Tags:
      server.address: localhost
      server.port: 44311
      http.request.method: GET
      url.scheme: https
      url.path: /Customer/Index
      network.protocol.version: 2
      http.route: {controller=Home}/{action=Index}/{id?}
      http.response.status_code: 200
  

This is in part due to the data provided by the OpenTelemetry.Instrumentation.AspNetCore library, where the configured pattern is used as http.route. This is a known issue in that library: open-telemetry/opentelemetry-dotnet-contrib#1730

Changes

• adjust TraceHelper to better handle cases where http.route contains a controller pattern.
• Add more test cases

With this change:

[vishweshbankwar]

@TimothyMothra Could you confirm if the output with this change matches with the output when exporter without this change is used with 1.6.0-beta.3 version of the instrumentation library?

[azure-sdk]

API change check

API changes are not detected in this pull request.

[bunkrur]

Thank you for this!

[insylogo]

Routes should not be fully populated in the names if you don't want to blow up cardinality on requests i.e. when you go to app insights, you should see something like /MyController/MyAction/{id} and not /MyController/MyAction/123, otherwise you can't get accurate statistics in most views for request timing etc.

It is of course better than /{Controller}/{Action}/{id}, and I'm not even sure how this populates all the route fields with these changes?

[TimothyMothra]

Closing this PR for now. Tracking the issue here: #41650
Were going to work with the OpenTelemetry community to see what fixes can be applied there.