appfollow: Strengthen types using WildValue.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

zerver/webhooks/appfollow/view.py

@@ -1,12 +1,12 @@
 # Webhooks for external integrations.
 import re
-from typing import Any, Dict
 
 from django.http import HttpRequest, HttpResponse
 
 from zerver.decorator import webhook_view
 from zerver.lib.request import REQ, has_request_variables
 from zerver.lib.response import json_success
+from zerver.lib.validator import WildValue, check_string, to_wild_value
 from zerver.lib.webhooks.common import check_send_webhook_message
 from zerver.models import UserProfile
 
@@ -16,9 +16,9 @@ from zerver.models import UserProfile
 def api_appfollow_webhook(
     request: HttpRequest,
     user_profile: UserProfile,
-    payload: Dict[str, Any] = REQ(argument_type="body"),
+    payload: WildValue = REQ(argument_type="body", converter=to_wild_value),
 ) -> HttpResponse:
-    message = payload["text"]
+    message = payload["text"].tame(check_string)
     app_name_search = re.search(r"\A(.+)", message)
     assert app_name_search is not None
     app_name = app_name_search.group(0)