ConnectionString not read from appsettings.json when using AddApplicationInsightsTelemetry(ApplicationInsightsServiceOptions)

[cijothomas]

Describe your environment. Describe any aspect of your environment relevant to the problem:

• SDK version: All
• .NET runtime version (.NET or .NET Core, TargetFramework in the .csproj file): .NET Core
• Hosting Info (IIS/Azure WebApps/etc):
• Platform and OS version:

If you're reporting a problem with a specific version of a library in this repo, please check whether the problem has been fixed on master.

Steps to reproduce.
Create a new Asp.Net Core App, follow doc to onboard to SDK.
Put ConnectionString in appsettings.json
Modify ConfigureServices.cs to enable AI as below:
var aiOptions = new ApplicationInsightsServiceOptions();
aiOptions.EnableSampling = false;
services.AddApplicationInsightsTelemetry(aiOptions);

What is the expected behavior?
ConnectionString should be still read from appsettings.json

What is the actual behavior?
What did you see instead?
ConnectionString was not read from appsettings.json, hence no telemetry was reported. VS debugger shows 'unconfigured' telemetry items locally.
Additional context.
Add any other context about the problem here.
services.AddApplicationInsightsTelemetry() is reading connectionstring as expected from appsettings.json