TACACS+: TLS Support for TACACS+ (TACACS+/TCP Secure Transport)

This feature enhances the existing TACACS+ over TCP (TACACS+/TCP) implementation by adding support for Transport Layer Security (TLS), enabling secure TACACS+ communication. With this update, the device-side TACACS+ client is extended to establish TLS sessions with TACACS+ servers, ensuring encryption of authentication, authorization, and accounting (AAA) traffic. The enhancement includes TLS handshake handling, server certificate validation, and secure session establishment, while maintaining backward compatibility with non-TLS configurations. This improves overall security by protecting sensitive data from interception and aligns TACACS+ communication with modern security standards.