rate_limit: Replace rate_limit with inlined rate limit checks.

This change incorporate should_rate_limit into rate_limit_user and
rate_limit_request_by_ip. Note a slight behavior change to other callers
to rate_limit_request_by_ip is made as we now check if the client is
eligible to be exempted from rate limiting now, which was previously
only done as a part of zerver.lib.rate_limiter.rate_limit.

Now we mock zerver.lib.rate_limiter.RateLimitedUser instead of
zerver.decorator.rate_limit_user in
zerver.tests.test_decorators.RateLimitTestCase, because rate_limit_user
will always be called but rate limit only happens the should_rate_limit
check passes;

we can continue to mock zerver.lib.rate_limiter.rate_limit_ip, because the
decorated view functions call rate_limit_request_by_ip that calls
rate_limit_ip when the should_rate_limit check passes.

We need to mock zerver.decorator.rate_limit_user for SkipRateLimitingTest
now because rate_limit has been removed. We don't need to mock
RateLimitedUser in this case because we are only verifying that
the skip_rate_limiting flag works.

To ensure coverage in add_logging_data, a new test case is added to use
a web_public_view (which decorates the view function with
add_logging_data) with a new flag to check_rate_limit_public_or_user_views.

Signed-off-by: Zixuan James Li <p359101898@gmail.com>

zilencer/auth.py

@@ -54,6 +54,9 @@ class InvalidZulipServerKeyError(InvalidZulipServerError):
 def rate_limit_remote_server(
     request: HttpRequest, remote_server: RemoteZulipServer, domain: str
 ) -> None:
+    if not should_rate_limit(request):
+        return
+
     try:
         RateLimitedRemoteZulipServer(remote_server, domain=domain).rate_limit_request(request)
     except RateLimited as e:
@@ -98,8 +101,7 @@ def authenticated_remote_server_view(
         except JsonableError as e:
             raise UnauthorizedError(e.msg)
 
-        if should_rate_limit(request):
-            rate_limit_remote_server(request, remote_server, domain="api_by_remote_server")
+        rate_limit_remote_server(request, remote_server, domain="api_by_remote_server")
         return view_func(request, remote_server, *args, **kwargs)
 
     return _wrapped_view_func