RoleBinding describes the roles that the subject have in Kalm system.
|subject||string||subject that is binding to role||True|
|subjectType||string||type of subject, can be: ||True|
|role||string||the role that this subject is binding to, can be: ||True|
|creator||string||Creator of this binding||True|
|expiredAt||*metav1.Time||Expire time of this key. Infinity if blank||False|