type NodeIdentifier interface {
// NodeIdentity determines node information from the given user.Info.// nodeName is the name of the Node API object associated with the user.Info,// and may be empty if a specific node cannot be determined.// isNode is true if the user.Info represents an identity issued to a node.
NodeIdentity(user.Info) (nodeName string, isNode bool)
}
NodeIdentifier determines node information from a given user
NewDefaultNodeIdentifier returns a default NodeIdentifier implementation,
which returns isNode=true if the user groups contain the system:nodes group
and the user name matches the format system:node:<nodeName>, and populates
nodeName if isNode is true