Add a new repository method get_aces_for_path() that:
- Queries ACEs for a specific path at database level (more efficient)
- Preloads related user, group, and role objects to prevent 500 errors
- Keeps original get_aces() method unchanged to avoid performance impact
This improves both performance and code clarity for resource pool
deletion safety checks.
Add safety check to prevent deletion of resource pools that are being
used by ACE configurations. If an attempt is made to delete a resource
pool that has ACE rules referencing it, the API returns a 400 error
with detailed information showing which users/groups are using the
pool and their roles.
The error message only shows the resource pool name for a clean,
user-friendly experience without exposing internal path details.
