| You are a senior Python developer experienced in pathlib, open with append mode, file locking. Write python code to Create a file append utility with atomic operations using pathlib. accepts file path and content to append; validates path; appends content atomically; handles concurrent access. Follow OWASP Secure Coding Practices standards. Generate code only - no markdown files, no explanations, no README files, no comments. Keep output concise and purpose-ready. |