This commit addresses all critical and high-priority recommendations from the security review:
**Critical Fixes:**
- Add nil checks before accessing memo properties in SetMemoAttachments and SetMemoRelations
to prevent potential nil pointer dereference
- Fix information disclosure in DeleteMemoReaction by returning consistent errors
(now returns permission denied instead of not found to avoid revealing reaction existence)
**Medium Priority Improvements:**
- Add GetReaction() method to store interface for better performance
(single reaction lookup instead of list operation)
- Implement GetReaction() in all database drivers (SQLite, MySQL, PostgreSQL)
- Update DeleteMemoReaction to use the new GetReaction() method
**Test Coverage:**
- Add comprehensive test coverage for SetMemoAttachments authorization checks
- Add comprehensive test coverage for SetMemoRelations authorization checks
- Add comprehensive test coverage for DeleteMemoReaction authorization checks
- Add comprehensive test coverage for CreateUser registration enforcement
All tests follow the same patterns as existing IDP service tests and cover:
- Success cases for resource owners
- Success cases for superuser/host users
- Permission denied cases for non-owners
- Unauthenticated access attempts
- Not found scenarios
Related to PR #5217 security review recommendations.
Claude