int manager_add_user(Manager *m, uid_t uid, gid_t gid, const char *name, User **_user);
int manager_add_user_by_name(Manager *m, const char *name, User **_user);
int manager_add_user_by_uid(Manager *m, uid_t uid, User **_user);
int manager_add_user(Manager *m, uid_t uid, gid_t gid, const char *name, User **_user);
int manager_add_user_by_name(Manager *m, const char *name, User **_user);
int manager_add_user_by_uid(Manager *m, uid_t uid, User **_user);