Missing APPLICATIONINSIGHTS_CONNECTION_STRING causes cryptic error during startup

[sylvaingirardbe]

Provide the steps required to reproduce the problem:

Create a function or logic app and try to run it in on 4.x runtime/host in a container where there's no APPLICATIONINSIGHTS_CONNECTION_STRING configured.

Expected behavior

The container does not start indicating that there's config (APPLICATIONINSIGHTS_CONNECTION_STRING) missing.

Actual behavior

Container doesn't start with this exception:
System.InvalidOperationException: Unable to resolve service for type 'Microsoft.ApplicationInsights.TelemetryClient' while attempting to activate 'Microsoft.Azure.Workflows.WebJobs.Extensions.Configuration.FlowFunctionConfiguration'.

Known workarounds

Add APPLICATIONINSIGHTS_CONNECTION_STRING to the config.