fix(fastapi): issue with APIRouter subclasses

Fixes: #3671

When an APIRouter subclass would overwrite the matches method with an implementation that depended
on non-standard fields existing on the HTTP connection scope, this would cause a failure when the
OpenTelemetryMiddleware tried to get the default span details for the incoming request. This has
been fixed by using the matches implementation on the Route class for any subclass of Route. This
should be sufficient since the only information we are trying to get from that method is the path
for the request.

Author: lannuttia

instrumentation/opentelemetry-instrumentation-fastapi/src/opentelemetry/instrumentation/fastapi/__init__.py

@@ -190,7 +190,7 @@ def client_response_hook(span: Span, scope: dict[str, Any], message: dict[str, A
 import fastapi
 from starlette.applications import Starlette
 from starlette.middleware.errors import ServerErrorMiddleware
-from starlette.routing import Match
+from starlette.routing import Match, Route
 from starlette.types import ASGIApp
 
 from opentelemetry.instrumentation._semconv import (
@@ -448,7 +448,11 @@ def _get_route_details(scope):
     route = None
 
     for starlette_route in app.routes:
-        match, _ = starlette_route.matches(scope)
+        match, _ = (
+            Route.matches(starlette_route, scope)
+            if isinstance(starlette_route, Route)
+            else starlette_route.matches(scope)
+        )
         if match == Match.FULL:
             route = starlette_route.path
             break