webhooks: Migrate webhooks with str parameters to use @typed_endpoint.

These webhooks have some URL query params that do not need additional
validation or parsing from JSON. So WebhookPaylaod is not applicable to
these webhooks.

zerver/webhooks/heroku/view.py

@@ -2,8 +2,8 @@
 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.typed_endpoint import typed_endpoint
 from zerver.lib.webhooks.common import check_send_webhook_message
 from zerver.models import UserProfile
 
@@ -17,15 +17,16 @@ TEMPLATE = """
 
 
 @webhook_view("Heroku", notify_bot_owner_on_invalid_json=False)
-@has_request_variables
+@typed_endpoint
 def api_heroku_webhook(
     request: HttpRequest,
     user_profile: UserProfile,
-    head: str = REQ(),
-    app: str = REQ(),
-    user: str = REQ(),
-    url: str = REQ(),
-    git_log: str = REQ(),
+    *,
+    head: str,
+    app: str,
+    user: str,
+    url: str,
+    git_log: str,
 ) -> HttpResponse:
     content = TEMPLATE.format(user=user, head=head, app=app, url=url, git_log=git_log)