Accept SecretStr as the Slack webhook URL

Allow the URL argument to SlackWebhookClient and SlackRouteErrorHandler
to be given as a SecretStr so that applications that get that value
from a SecretStr field of their configuration don't have to convert
it first.

changelog.d/20240717_223040_rra_DM_45281_queue.md

@@ -0,0 +1,3 @@
+### New features
+
+- Allow the Slack webhook URL argument to `SlackWebhookClient` and `SlackRouteErrorHandler` to be given as a Pydantic `SecretStr` instead of a `str`. This simplifies code in applications that get that value from a secret.

src/safir/slack/webhook.py

@@ -8,6 +8,7 @@
 from fastapi import HTTPException, Request, Response
 from fastapi.exceptions import RequestValidationError
 from fastapi.routing import APIRoute
+from pydantic import SecretStr
 from starlette.exceptions import HTTPException as StarletteHTTPException
 from structlog.stdlib import BoundLogger
 
@@ -56,9 +57,12 @@ class SlackWebhookClient:
     """
 
     def __init__(
-        self, hook_url: str, application: str, logger: BoundLogger
+        self, hook_url: str | SecretStr, application: str, logger: BoundLogger
     ) -> None:
-        self._hook_url = hook_url
+        if isinstance(hook_url, SecretStr):
+            self._hook_url = hook_url.get_secret_value()
+        else:
+            self._hook_url = hook_url
         self._application = application
         self._logger = logger
 
@@ -175,7 +179,7 @@ class SlackRouteErrorHandler(APIRoute):
 
     @classmethod
     def initialize(
-        cls, hook_url: str, application: str, logger: BoundLogger
+        cls, hook_url: str | SecretStr, application: str, logger: BoundLogger
     ) -> None:
         """Configure Slack alerting.
 

tests/slack/webhook_test.py

@@ -8,6 +8,7 @@
 import structlog
 from fastapi import APIRouter, FastAPI
 from httpx import ASGITransport, AsyncClient
+from pydantic import SecretStr
 
 from safir.datetime import current_datetime, format_datetime_for_logging
 from safir.slack.blockkit import SlackException, SlackMessage
@@ -44,7 +45,7 @@ async def test_post(mock_slack: MockSlackWebhook) -> None:
 @pytest.mark.asyncio
 async def test_post_exception(mock_slack: MockSlackWebhook) -> None:
     logger = structlog.get_logger(__file__)
-    client = SlackWebhookClient(mock_slack.url, "App", logger)
+    client = SlackWebhookClient(SecretStr(mock_slack.url), "App", logger)
 
     exc = SlackException("Some exception message")
     await client.post_exception(exc)