SnAclEditor sets permissions for SystemUser #2204
Description
In SnAclEditor.ApplyAync method, there is a validation that logs a warning:
Invalid ACL: ace identity is 'Node not found. Id: -1', which means that the SystemUser's permissions were tried to be set.
Despite this, the permission is written to the database (IdentityId column of the EFEntries table contains -1).
Expectation: SystemUser permissions should not be persisted.