can configure otel service name

[scrocquesel-ml150]

What problem would the feature you're requesting solve? Please describe.

Our function name are a bit meaningless and we use OTEL_SERVICE_NAME to override the value of service.name in the isolated worker process.
Unfortunately, FunctionsResourceDetector use WEBSITE_SITE_NAME which is a read-only settings.

azure-functions-host/src/WebJobs.Script/Diagnostics/OpenTelemetry/FunctionsResourceDetector.cs

Line 18 in 64bc0b3

string serviceName = Environment.GetEnvironmentVariable(OpenTelemetryConstants.SiteNameEnvVar);

When searching transaction in appInsights, we have two differents values for the service name depending the source of the trace (host or worker).

Describe the solution you'd like

Provide a configurable setting to override the WEBSITE_SITE_NAME. For example, the worker use WEBSITE_CLOUD_ROLENAME

https://github.com/Azure/azure-functions-dotnet-worker/blob/ab7b3f25a6cd706aa9906c11b2feced98f59e273/src/DotNetWorker.ApplicationInsights/Initializers/AppServiceOptionsInitializer.cs#L9

[scrocquesel-ml150]

As additional context, be aware that the Azure Portal is using WEBSITE_SITE_NAME for the invocation logs page. So, invocations do not show up anymore. This is already the case when telemetryMode is ApplicationInsights.