docs: public Collection<GrantedAuthority> getGrantedAuthorities(DirContextOperations user, String username) {
          String userDn = user.getNameInNamespace();
  
          if (logger.isDebugEnabled()) {
              logger.debug("Getting authorities for user " + userDn);
          }
  
          Set<GrantedAuthority> roles = getGroupMembershipRoles(userDn, username);
  
          Set<GrantedAuthority> extraRoles = getAdditionalRoles(user, username);
  
          if (extraRoles != null) {
              roles.addAll(extraRoles);
          }
  
          if (defaultRole != null) {
              roles.add(defaultRole);
          }
  
          List<GrantedAuthority> result = new ArrayList<GrantedAuthority>(roles.size());
          result.addAll(roles);
  
          return result;
      }