fix(service-accounts): Don't look up a member limit with no user (#129906)

`is_member_disabled_from_limit` now returns False for a caller with no
user, before any membership lookup. Seat limits apply to members, and a
service account isn't one.

The function takes an `HttpRequest`, so the `request.user` mypy check
didn't cover its `user.id` read. Sentry's own permission classes pass an
`RpcUserOrganizationContext` and never reach that read. getsentry's
customer details endpoint passes a DRF request with an `Organization`,
which goes to `check_membership_by_id(user_id=user.id)`. A service
account with `org:billing` gets 403 `user-required` there today, from
the `ServiceAccountId` guard. Once #129763 removes the guard, it gets a
500. Passing `acting_user_id` instead would send `None` into a lookup
that matches pending invites, so the function returns early.

The new test on master:

```
E   sentry.api.exceptions.UserRequired: {'detail': {'code': 'user-required', 'message': 'This action requires a user.', 'extra': {}}}
FAILED tests/sentry/api/test_utils.py::IsMemberDisabledFromLimitTest::test_service_account_is_not_a_limited_member
```

With the fix, the API utils, organization permission and permissions
suites pass (214 tests).

Author: gricha

src/sentry/api/utils.py

@@ -23,6 +23,7 @@
 
 from sentry import options, quotas
 from sentry.api.exceptions import ResourceDoesNotExist
+from sentry.auth.principal import has_user
 from sentry.auth.staff import is_active_staff
 from sentry.auth.superuser import is_active_superuser
 from sentry.db.models.fields.bounded import BoundedBigAutoField
@@ -307,7 +308,9 @@ def is_member_disabled_from_limit(
     if is_active_superuser(request) or is_active_staff(request):
         return False
 
-    # must be a simple user at this point
+    # Only a member can be limited; with no user, a membership lookup would match pending invites.
+    if not has_user(user):
+        return False
 
     member: RpcOrganizationMember | None
     if isinstance(organization, RpcUserOrganizationContext):

tests/sentry/api/test_utils.py

@@ -1,5 +1,6 @@
 import datetime
 import unittest
+from typing import Any
 from unittest.mock import MagicMock, patch
 
 import pytest
@@ -16,12 +17,14 @@
     clamp_date_range,
     get_date_range_from_params,
     handle_query_errors,
+    is_member_disabled_from_limit,
     print_and_capture_handler_exception,
     to_valid_int_id,
     to_valid_int_id_list,
 )
 from sentry.db.models.fields.bounded import BoundedBigAutoField
 from sentry.exceptions import IncompatibleMetricsQuery, InvalidParams, InvalidSearchQuery
+from sentry.service_accounts.principal import ServiceAccountPrincipal
 from sentry.testutils.cases import APITestCase
 from sentry.testutils.helpers.datetime import freeze_time
 from sentry.utils.snuba import (
@@ -336,6 +339,17 @@ def test_handle_snuba_rpc_bad_request(self, mock_capture_exception: MagicMock) -
         mock_capture_exception.assert_called_once_with(error)
 
 
+class IsMemberDisabledFromLimitTest(APITestCase):
+    def test_service_account_is_not_a_limited_member(self) -> None:
+        request = self.make_request()
+        principal: Any = ServiceAccountPrincipal(
+            service_account_id=1, organization_id=self.organization.id, name="sa"
+        )
+        request.user = principal
+
+        assert is_member_disabled_from_limit(request, self.organization) is False
+
+
 class ClampDateRangeTest(unittest.TestCase):
     def test_no_clamp_if_range_under_max(self) -> None:
         start = datetime.datetime(2024, 1, 1)