joinGroup method
Joining a group
If a player joins a public group they immediately become a member, but if they try and join a private group they must be accepted by a group admin.
Players can join a group.
Implementation
@override
Future<void> joinGroup({
required model.Session session,
required String groupId,
}) async {
_session = session;
await _api.v2GroupGroupIdJoinPost(groupId: groupId);
}