Revert "Move auth metrics reporting to a background task"

This reverts commit 2d0ea93.
The problem will be fixed in the next release of Safir in the
underlying metrics code by backgrounding the write inside the
metrics layer.

src/gafaelfawr/handlers/ingress.py

@@ -12,15 +12,8 @@
 from datetime import timedelta
 from typing import Annotated
 
-from fastapi import (
-    APIRouter,
-    BackgroundTasks,
-    Depends,
-    Header,
-    HTTPException,
-    Query,
-    Response,
-)
+import sentry_sdk
+from fastapi import APIRouter, Depends, Header, HTTPException, Query, Response
 from safir.datetime import current_datetime
 from safir.models import ErrorModel
 from safir.slack.webhook import SlackRouteErrorHandler
@@ -34,7 +27,7 @@
 from ..constants import MINIMUM_LIFETIME
 from ..dependencies.auth import AuthenticateRead
 from ..dependencies.context import RequestContext, context_dependency
-from ..events import AuthBotEvent, AuthUserEvent, FrontendEvents
+from ..events import AuthBotEvent, AuthUserEvent
 from ..exceptions import (
     ExternalUserInfoError,
     InsufficientScopeError,
@@ -312,30 +305,6 @@ async def authenticate_with_type(
     return await authenticate(context=context)
 
 
-async def publish_auth_event(
-    events: FrontendEvents, auth_config: AuthConfig, token_data: TokenData
-) -> None:
-    """Publish metrics events for a successful authentication.
-
-    Parameters
-    ----------
-    events
-        Event manager.
-    auth_config
-        Requested authentication parameters.
-    token_data
-        Successful authentication data.
-    """
-    username = token_data.username
-    service = auth_config.service
-    if is_bot_user(token_data.username):
-        bot_event = AuthBotEvent(username=username, service=service)
-        await events.auth_bot.publish(bot_event)
-    else:
-        user_event = AuthUserEvent(username=username, service=service)
-        await events.auth_user.publish(user_event)
-
-
 @router.get(
     "/ingress/auth",
     description="Meant to be used as an NGINX auth_request handler",
@@ -353,7 +322,6 @@ async def get_auth(
     token_data: Annotated[TokenData, Depends(authenticate_with_type)],
     context: Annotated[RequestContext, Depends(context_dependency)],
     response: Response,
-    background_tasks: BackgroundTasks,
 ) -> dict[str, str]:
     check_lifetime(context, auth_config, token_data)
 
@@ -392,9 +360,18 @@ async def get_auth(
     headers = await build_success_headers(context, auth_config, token_data)
     for key, value in headers:
         response.headers.append(key, value)
-    background_tasks.add_task(
-        publish_auth_event, context.events, auth_config, token_data
-    )
+
+    # Send a metric event for the authentication.
+    with sentry_sdk.start_span(name="events.publish"):
+        username = token_data.username
+        service = auth_config.service
+        if is_bot_user(username):
+            bot_event = AuthBotEvent(username=username, service=service)
+            await context.events.auth_bot.publish(bot_event)
+        else:
+            user_event = AuthUserEvent(username=username, service=service)
+            await context.events.auth_user.publish(user_event)
+
     return {"status": "ok"}