Struct representing a lifecycle event from Group.
Events are delivered as {:group, events, info} tuples to processes
that called Group.monitor/2.
Fields
:type- Event type::registered,:unregistered,:joined, or:left:supervisor- The supervisor name:cluster- The cluster name (nilfor default cluster):key- The key that triggered the event:pid- The process involved:meta- User-provided metadata (internal keys stripped):previous_meta- Previous metadata on re-register/re-join (nilif new):reason- Exit reason on:unregistered/:leftevents