What is missing?

The OpenStack DNS (Designate) API v2 supports TSIG keys for authenticating DNS transactions between
servers, but gophercloud currently has no support for this resource.

This issue proposes adding a new package to manage TSIG keys, including basic CRUD operations (List, Get,
Create, Update, Delete), following existing DNS v2 patterns.

Reference: https://docs.openstack.org/api-ref/dns/dns-api-v2-index.html#tsigkey