[BUG] Deployed flex flow does not log dependencies to App Insights

[jomalsan]

Describe the bug
When deploying a prompt flow to Azure Container Apps (ACA), with Authentication turned on, I receive trace messages (logs) in Application Insights but do not get dependencies that track the flow execution. This is observed when using the built in UI.

I noticed that if I call the /score endpoint with OTel traceparent set with trace flag 01, that it works as expected and I see logs and dependencies. With a trace flag of 00 or with the header omitted then I see only traces.

I suspect that the underlying issue is in the PF handling of the traceparent header, and that ACA is just showing this issue. I would expect that regardless of the trace flag, I should be seeing my dependency information show up.

When running the docker image locally, I get all expected telemetry regardless of the traceparent header.

How To Reproduce the bug
Steps to reproduce the behavior:

1. Create a flow
2. Package the flow in the docker format
3. Build the docker image (and push to an ACR)
4. Define an Azure Container App based on the image
5. Enable Authentication
6. Use the built in PF UI to make a request. I

Expected behavior
Consistent logging to application insights regardless of the hosting environment of the built docker image.

Running Information(please complete the following information):
{
"promptflow": "1.15.0",
"promptflow-azure": "1.15.0",
"promptflow-core": "1.15.0",
"promptflow-devkit": "1.15.0",
"promptflow-tracing": "1.15.0"
}

Python (Darwin) 3.11.9 (v3.11.9:de54cf5be3, Apr 2 2024, 07:12:50)

Additional context
Adding a trace parent header to start the span in the deployed UI with the appropriate trace flag could be an easy fix to this