TURN server security best practices + coturn hardening guide

[Sandro Gauci]

Published two guides on TURN server security:

1. Implementation-agnostic best practices covering IP range blocking, protocol hardening, rate limiting, and deployment patterns for SFU-first vs P2P architectures: https://www.enablesecurity.com/blog/turn-security-best-practices/

2. coturn-specific configuration guide with three complete config templates (minimal to high-security): https://www.enablesecurity.com/blog/coturn-security-configuration-guide/

Config templates are also on GitHub with a Docker test environment for validation: https://github.com/EnableSecurity/coturn-secure-config

These are companions to the TURN security threats analysis published earlier this month.