webhooks: Migrate most webhooks to use @typed_endpoint.

This converts most webhook integration views to use @typed_endpoint instead
of @has_request_variables, rewriting REQ parameters. For these
webhooks, it simply requires switching the decorator, rewriting the
type annotation of payload/message to WebhookPayload[WildValue], and
removing the REQ default that defines the to_wild_value converter.

zerver/webhooks/greenhouse/view.py

@@ -1,16 +1,9 @@
 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_int,
-    check_none_or,
-    check_string,
-    check_url,
-    to_wild_value,
-)
+from zerver.lib.typed_endpoint import WebhookPayload, typed_endpoint
+from zerver.lib.validator import WildValue, check_int, check_none_or, check_string, check_url
 from zerver.lib.webhooks.common import check_send_webhook_message
 from zerver.models import UserProfile
 
@@ -38,11 +31,12 @@ def dict_list_to_string(some_list: WildValue) -> str:
 
 
 @webhook_view("Greenhouse")
-@has_request_variables
+@typed_endpoint
 def api_greenhouse_webhook(
     request: HttpRequest,
     user_profile: UserProfile,
-    payload: WildValue = REQ(argument_type="body", converter=to_wild_value),
+    *,
+    payload: WebhookPayload[WildValue],
 ) -> HttpResponse:
     action = payload["action"].tame(check_string)
     if action == "ping":