Spans for FastAPI background tasks are not shown as async

[antonpirker]

How do you use Sentry?

Sentry Saas (sentry.io)

Version

all

Steps to Reproduce

Use this example FastAPI app:
https://github.com/antonpirker/testing-sentry/tree/main/test-fastapi-background-tasks

It calls a number of FastAPI background tasks when you point your browser to http://localhost:5000

This was reported by a user. See:
https://sentry.sentry.io/feedback/?referrer=slack&notification_uuid=83102b8eed5a-4b4[…]ype=issue&feedbackSlug=javascript%3A5697577869&project=11276

Expected Result

The spans that are created for the background tasks should be in parallel, because those background tasks are called asynchronously by FastAPI.
NOTE: this needs to be checked in the FastAPI source code if it is actually calling those background tasks in parallel! (maybe this is the correct result...)

Actual Result

The spans are shown as being executed in serial: