API crash because of bad URL parameters

## Acceptance criteria

- [ ] URL matching or view logic prevents an error with a proper 4xx response.

---

Sentry Issue: [FLAGSMITH-API-5NF](https://flagsmith.sentry.io/issues/7447801569/?referrer=github_integration)

```
ValueError: invalid literal for int() with base 10: 'org_3COWhASRXfhcdxVrd0wEjpQp4dg'
File "django/db/models/fields/__init__.py", line 2128, in get_prep_value
return int(value)

ValueError: Field 'id' expected a number but got 'org_3COWhASRXfhcdxVrd0wEjpQp4dg'.
(17 additional frame(s) were not displayed)
...
File "features/views.py", line 861, in get_queryset
return super().get_queryset().filter(identity__pk=self.kwargs["identity_pk"]) # type: ignore[no-untyped-call]
```

Contributes to #6809