webhooks: Migrate transifex to use endpoint to use @typed_endpoint.

Transifex has parameters that need to be parsed from JSON and converted
to int. Note that we use Optional[Json[int]] instead of
Json[Optional[int]] to replicate the behavior of json_validator. This
caveat is explained in a new test called test_json_optional.

zerver/tests/test_typed_endpoint.py

@@ -546,6 +546,23 @@ class TestEndpoint(ZulipTestCase):
 
         call_endpoint(test_view, HostRequestMock({"foo": ""}))
 
+    def test_json_optional(self) -> None:
+        # Optional[Json[int]] does not allow client provided optional value at
+        # all. The only possible way for val to be None is through the default
+        # value (if it has one).
+        @typed_endpoint
+        def foo(request: HttpRequest, *, val: Optional[Json[int]]) -> None:
+            ...
+
+        # Json[Optional[int]] however, allows client specified None value.
+        @typed_endpoint
+        def bar(request: HttpRequest, *, val: Json[Optional[int]]) -> None:
+            ...
+
+        with self.assertRaisesMessage(ApiParamValidationError, "val is not an integer"):
+            call_endpoint(foo, HostRequestMock({"val": orjson.dumps(None).decode()}))
+        call_endpoint(bar, HostRequestMock({"val": orjson.dumps(None).decode()}))
+
 
 class ValidationErrorHandlingTest(ZulipTestCase):
     def test_special_handling_errors(self) -> None:

zerver/webhooks/transifex/view.py

@@ -2,12 +2,12 @@
 from typing import Optional
 
 from django.http import HttpRequest, HttpResponse
+from pydantic import Json
 
 from zerver.decorator import webhook_view
 from zerver.lib.exceptions import UnsupportedWebhookEventTypeError
-from zerver.lib.request import REQ, has_request_variables
 from zerver.lib.response import json_success
-from zerver.lib.validator import check_int
+from zerver.lib.typed_endpoint import typed_endpoint
 from zerver.lib.webhooks.common import check_send_webhook_message
 from zerver.models import UserProfile
 
@@ -15,15 +15,16 @@ All_EVENT_TYPES = ["translated", "review"]
 
 
 @webhook_view("Transifex", notify_bot_owner_on_invalid_json=False, all_event_types=All_EVENT_TYPES)
-@has_request_variables
+@typed_endpoint
 def api_transifex_webhook(
     request: HttpRequest,
     user_profile: UserProfile,
-    project: str = REQ(),
-    resource: str = REQ(),
-    language: str = REQ(),
-    translated: Optional[int] = REQ(json_validator=check_int, default=None),
-    reviewed: Optional[int] = REQ(json_validator=check_int, default=None),
+    *,
+    project: str,
+    resource: str,
+    language: str,
+    translated: Optional[Json[int]] = None,
+    reviewed: Optional[Json[int]] = None,
 ) -> HttpResponse:
     topic = f"{project} in {language}"
     if translated: