otel Datadog exporter is not propagating trace context from upstream spans

[samuelAndalon]

Describe the bug

Datadog is not showing parent spans of the router callers, it only shows downstream spans

in our distributed system there are 2 services on top of the router:

after some debugging found that, ServiceB is properly sending x-datadog-trace-id and x-datadog-parent-id, the issue not there, it seems that problem is that the custom Apollo DatadogExporter is not assigning the x-datadog-parent-id value after it gets extracted to the span parent id.

if I send a graphQL request to the router with these DD headers.

the headers are properly extracted:

however here is where issue starts:

The custom Apollo oTel Datadog exporter is wrongly assigning x-datadog-parent-id as span-id of the incoming request span, see:
https://github.com/apollographql/router/blob/main/apollo-router/src/plugins/telemetry/tracing/datadog_exporter/mod.rs#L400

The SpanData struct has a parent_span_id field, and a span_context, this span context is the one that exposes the span_id and the trace_id.

Expected behavior

Datadog should show all the spans that belong to a given trace-id, included upstream services that are calling the router.