Collection<? extends GrantedAuthority> getReachableGrantedAuthorities(Collection<? extends GrantedAuthority> authorities)
Reachable authorities are the directly assigned authorities plus all authorities that are (transitively) reachable from them in the role hierarchy.
Role hierarchy: ROLE_A > ROLE_B and ROLE_B > ROLE_C.
Directly assigned authority: ROLE_A.
Reachable authorities: ROLE_A, ROLE_B, ROLE_C.
authorities- - List of the directly assigned authorities.