Next-Gen WAF: Error responses now documented for all endpoints

Several Next-Gen WAF API endpoints were missing documentation for error response codes they can return. Endpoints across Agents, Agent Keys, Custom Dashboards, Events, Lists, Rate Limited Sources, Redactions, Reports, Requests, Rules, Signals, Simulate, Thresholds, Timeseries, Virtual Patches, Workspace Alerts, and Workspaces now document the full set of error responses they can return.