Fastapi traces not captured for sub applications

[graham-atom]

We recently upgraded to version 2.14.4 for our fastapi application (fastapi = "0.111.0"). We were using the asgi integration with trace middleware https://ddtrace.readthedocs.io/en/stable/integrations.html#asgi but it seems to be deprecated in newer versions (even though the docs say nothing of this).

we mount a sub application like so:

from fastapi import Depends, FastAPI
app = FastAPI(
    title="API",
    version="1.0,0,
    docs_url=None,
    redoc_url=None,
    openapi_url=None,
    lifespan=lifespan,
)

from application.partner import partner_api

# "Mount" the Partner Endpoint API as a subapp at a subpath
SUB_APP_PREFIX = "/partner"
app.mount(SUB_APP_PREFIX, partner_api)

we run the application using ddtrace-run and the top level application traces appear, but none of the sub application