Prevent wildcard deletion in deleteUser/deleteRole methods

[Copilot]

Empty string parameters in deleteUser(), deleteRole(), and related methods act as wildcards in removeFilteredPolicy, causing all policies to be deleted instead of filtering by the specified user/role. This results in destructive SQL queries like DELETE FROM casbin_rule WHERE ptype = 'p'.

Changes

• Input validation: Added checks to reject empty/falsy parameters in:
  • deleteUser(), deleteRole(), deletePermission()
  • deleteRoleForUser(), deleteRolesForUser(), deletePermissionsForUser(), deletePermissionForUser()
• Error messages: Throw descriptive errors (e.g., "user must not be empty") instead of silently deleting all data
• Test coverage: Added tests verifying empty string, undefined, and null are rejected

Example

// Before: Silently deletes ALL policies
await enforcer.deleteUser('');

// After: Throws "user must not be empty"
await enforcer.deleteUser('');

The fix catches empty strings, undefined, and null at the API boundary before they reach the filtering logic.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>enforcer.deleteUser() wiped out all data from casbin_rule table</issue_title>
<issue_description>Logged queries shows that following queries are executed when calling enforcer.deleteUser()

DELETE from casbin_rule WHERE ptype = 'p';
DELETE from casbin_rule WHERE ptype = 'g'; 
```</issue_description>

## Comments on the Issue (you are @copilot in this section)

<comments>
</comments>

• Fixes enforcer.deleteUser() wiped out all data from casbin_rule table #462

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