pub const PLUGIN_API_VERSION_V2: u32 = 2;Expand description
API version v2: adds set_metric_recorder so plugins can emit
Prometheus metrics through the hub’s existing recorder. Plugins
built against v2 keep loading on v1 hubs (the hub ignores the field
because it doesn’t know it exists); plugins built against v1 keep
loading on v2 hubs (the hub gates access on api_version >= 2 and
skips the install for v1 plugins).