[Bug]: Reserved SQL keyword "key" not escaped in permission-aware queries for non-admins

[schaetzle]

Expected behavior

A new search or a saved search using the Advanced Object Search Bundle should work for both admin and non-admin users, regardless of the field names used in the object class (including fields named key).

Actual behavior

When a non-admin user executes a saved search on a class that contains a field named key, the system returns an HTTP 500 error. The stack trace shows a SQL syntax error caused by the unescaped usage of the reserved keyword key in a dynamically built permission-related SQL condition.

Excerpt from error:
SQLSTATE[42000]: Syntax error or access violation: 1064 You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'key),cpath)=1 ORDER BY LENGTH(cpath) DESC LIMIT 1)=1' at line 2
The issue does not occur for admin users, as permission filtering behaves differently.

Steps to reproduce

1. Create a DataObject class (e.g. Product) and add a field with the technical name key
2. Create a saved search using the Advanced Object Search interface
3. Assign the search to be usable by non-admin users
4. Log in as a non-admin user and load the saved search

Observe the HTTP 500 error in the browser and check the logs for SQL errors