Yang data model for Terminal Access Controller Access Control System Plus

This document defines two YANG modules that augment the System data model defined in the [RFC 7317] with TACACS+ client model and additional AAA model. The data model of Terminal Access Controller Access Control System Plus (TACACS+) client allows the configuration of TACACS+ servers for centralized Authentication, Authorization and Accouting. While the current system model only supports authentication configuration, the additional AAA model allows system authorization and accouting configuration. The YANG modules in this document conforms to the Network Management Datastore Architecture (NMDA) defined in [RFC8342].