Make cartServiceFailure 1/10th configurable

[agardnerIT]

Feature Request

Is your feature request related to a problem?

In demo scenarios, I want to make the problem appear faster.

Describe the solution you'd like:

Make the 1/10th failure configurable. It is currently hardcoded.

opentelemetry-demo/src/cartservice/src/services/CartService.cs

Line 66 in 395f385

if (await _featureFlagHelper.GetBooleanValue("cartServiceFailure", false) && random.Next(10) == 0)

Describe alternatives you've considered.

Which alternative solutions or features have you considered?

Additional Context

Feel free to add any other context about the feature request here.