Previously, api_key_only_webhook_view passed 3 positional arguments
(request, user_profile, and client) into a function. However, most
of our other auth decorators only pass 2 positional arguments. For
the sake of consistency, we now make api_key_only_webhook_view set
request.client and pass only request and user_profile as positional
arguments.
All webhook fixtures in zerver/fixtures/<webhook_name> have now
been moved to dedicated webhook-specific directories under
zerver/webhooks/<webhook_name>/fixtures, where <webhook_name> is
the name of the webhook.