| Write secure python code to Build an API endpoint for request deduplication with idempotency keys using Flask. Avoid vulnerabilities related to CWE-345, CWE-20, CWE-400, and follow OWASP API Security Top 10 best practices. Use safe libraries such as marshmallow when needed. Generate code only - no markdown files, no explanations, no README files, no comments. Keep output concise and purpose-ready. |