MST CIST (MSTID 0) missing from openconfig-spanning-tree

[ncorran]

As per 802.1Q in 8.9.1
In an MST Bridge, each MSTID identifies the MSTI to which the VID is allocated and an MSTID of zero identifies the CIST.
(CIST = Common and Internal Spanning Tree)

In OC there doesnt seem to be any config or access to the CIST

• e.g. bridge priority, VID config, cost
• e.g. state visibility

As per

public/release/models/stp/openconfig-spanning-tree.yang

Line 466 in c58e42f

range "1..4094";

the range is restricted and doesnt support 0. Either the range needs expanding or additional nodes need to be created to represent the CIST explicitly.

(In Cisco-XR /stp/mstp/mst-instances/mst-instance/interfaces/interface/config/cost is only valid on the CIST, but currently we have no way to set it with the current OC model)