Complete folder anatomy for all 649 cybersecurity skills + update LICENSE to Mahipal

- Add scripts/agent.py and references/api-reference.md to all remaining skills
- Update all 648 LICENSE files: copyright now reads 'Mahipal'
- Add implementing-security-monitoring-with-datadog (new skill with full anatomy)
- All 649 skills now have: SKILL.md, LICENSE, scripts/agent.py, references/api-reference.md

skills/testing-for-xml-injection-vulnerabilities/references/api-reference.md

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+# API Reference: Testing for XML Injection Vulnerabilities
+
+## XXE Payload Types
+
+| Payload | Severity | Description |
+|---------|----------|-------------|
+| File read (Linux) | Critical | `file:///etc/passwd` entity inclusion |
+| File read (Windows) | Critical | `file:///c:/windows/win.ini` entity |
+| SSRF via HTTP | Critical | Entity fetching internal metadata URL |
+| Parameter entity | High | External DTD loading via `%entity` |
+| Billion laughs | High | Recursive entity expansion (DoS) |
+| UTF-7 encoding | High | Encoding bypass for WAF evasion |
+
+## XPath Injection Payloads
+
+| Payload | Purpose |
+|---------|---------|
+| `' or '1'='1` | Boolean-based auth bypass |
+| `'] \| //user/password \| //foo['` | Data extraction via union |
+| `1 or 1=1` | Numeric context injection |
+
+## Detection Indicators
+
+| Attack | Success Indicator |
+|--------|-------------------|
+| Linux file read | `root:` in response body |
+| Windows file read | `[fonts]` or `extensions` in response |
+| SSRF metadata | `ami-id` or `instance-id` in response |
+| Billion laughs | Response time > 5 seconds |
+| Content-type switch | XML accepted when JSON expected |
+| SVG XXE | `root:` in upload response |
+
+## Python Libraries
+
+| Library | Version | Purpose |
+|---------|---------|---------|
+| `requests` | >=2.28 | HTTP POST with XML payloads |
+| `json` | stdlib | Report generation |
+| `pathlib` | stdlib | Output directory management |
+
+## References
+
+- OWASP XXE Prevention: https://cheatsheetseries.owasp.org/cheatsheets/XML_External_Entity_Prevention_Cheat_Sheet.html
+- PortSwigger XXE: https://portswigger.net/web-security/xxe
+- PayloadsAllTheThings XXE: https://github.com/swisskyrepo/PayloadsAllTheThings/tree/master/XXE%20Injection